DOCSLIB.ORG

Finding the Final Pieces of the Vitamin B12 Biosynthetic Jigsaw

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Finding the Final Pieces of the Vitamin B12 Biosynthetic Jigsaw COMMENTARY Finding the final pieces of the vitamin B12 biosynthetic jigsaw Martin J. Warren* Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom ver since Dorothy Hodgkin gate anaerobe Eubacterium limosum min B12 deficiency in the photosynthetic solved the structure of vitamin (13). Here, labeling revealed that the bacterium Rhodobacter capsulatus (18). B12 some 50 years ago, research- DMB framework was synthesized anaer- Campbell et al. (1) demonstrate that ers have been puzzling over how obically from erythrose, glycine, for- their S. meliloti bluB mutant strain is Ethis amazing molecular jigsaw is pieced mate, glutamine, and methionine. also a B12 auxotroph but, more specifi- together. In essence, vitamin B12 is However, as with the synthesis of the cally, that it is deficient in the biosyn- a modified tetrapyrrole (corrinoid ring) corrin ring, it also was noted that some thesis of DMB. There appears to be to which is attached either an upper ad- organisms synthesized DMB aerobically a certain amount of serendipity in the enosyl or methyl group and a lower and required molecular oxygen to allow isolation of their bluB strain, because base, usually dimethylbenzimidazole its synthesis (14). In the aerobic path- there is no obvious connection between (DMB) (Fig. 1). Although significant way, it was shown that riboflavin is a requirement for B12 and the produc- success has been achieved toward an transformed into DMB through FMN tion of succinyloglycan. The blu prefix understanding of the construction of the (15) (Fig. 1). This amazing transforma- refers to the fact that the blu genes are corrin ring component of the coenzyme, tion, for which no precedent exists in required to make an aerobic culture of there has been a paucity of information chemistry, sees the C-2 carbon of DMB R. capsulatus blush (i.e., produce photo- concerning the biosynthesis of DMB. In derived from the C1 of the ribose moi- synthetic pigments) after reduction of a recent issue of PNAS, Campbell et al. ety of FMN (16, 17). Significantly, how- the pO2. This earlier research demon- (1) identified an enzyme that appears to ever, no genes or enzymes involved in strated that a bluB strain could be cor- play a key role in the transformation of either the aerobic or anaerobic biosyn- rected by the addition of vitamin B12 flavin into DMB. thesis of DMB have been identified but not by cobinamide (i.e., vitamin B12 missing the lower base). This finding Vitamin B12 is best known as the anti- so far. pernicious anemia factor, which was first suggests two things: (i) that bluB is identified 80 years ago in crude liver somehow involved in either the synthesis extracts (2) before its subsequent purifi- There appears of DMB or its attachment to the corrin cation in 1948 (3) and structure deter- ring framework, and (ii) that the biosyn- mination in 1955 (4). There are two to be a certain amount thesis of vitamin B12 somehow disturbs the biosynthesis of bacteriochlorophyll. features that make vitamin B12 stand out in comparison with all other nutri- of serendipity in In the case of the latter, strong evidence ents. First, it is made only by microbes was subsequently presented to demon- (5, 6) (seemingly its biosynthetic soft- the isolation of strate that vitamin B12 may well be ware never made the prokaryotic to required for the biosynthesis of the iso- eukaryotic transition), and second, there Campbell et al.’s cyclic ring of bacteriochlorophyll (19). is the sheer complexity of its synthesis, Perhaps we should not be surprised to which requires Ϸ30 enzyme-mediated bluB strain. find that BluB is involved in DMB bio- steps (7). The latter part of the 20th synthesis, because evidence that BluB century saw a major effort to elucidate was involved in DMB biosynthesis was the biosynthesis of this remarkable co- Campbell et al. (1) were not actually presented in a patent application, which claimed that overproduction of BluB led factor. A multidisciplinary approach trying to investigate B12 biosynthesis. involving microbiology, genetics, recom- They were studying aspects of polysac- to raised levels of DMB (20). This find- binant DNA technology, NMR, and charide synthesis in Rhizobia, the soil ing is significant because DMB is nor- chemistry saw the dissection of this bacteria that live in specialized root mally limiting in the biosynthesis of vitamin B . Thus, before the work by complex metabolic pathway (8–10). Of nodules of leguminous plants. As part of 12 Campbell et al. (1), there was evidence course, things were more complicated their symbiotic relationship with the that BluB was required for the aerobic than anticipated. It was found that there plant, the bacteria produce fixed nitro- synthesis of the lower axial base. How- were two distinct pathways for cobal- gen in return for carbon compounds. ever, what Campbell et al. were able to amin biosynthesis, representing aerobic During the invasion of the plant nod- do was to show that a mutant in bluB and anaerobic routes (11). Although the ules, the bacteria produce an acidic was able to grow in the presence of aerobic route for corrin ring assembly exopolysaccharide, termed succinogly- either vitamin B or DMB but not in was elucidated, the secrets of the anaer- can. They devised a rapid genetic screen 12 the presence of cobinamide. They also obic process have yet to be determined. for Sinorhizobium meliloti that allowed showed that bluB mutants accumulated them to identify bacteria that were ei- The attachment of the lower nucleotide GDP–cobinamide, the immediate pre- ther deficient in the production of succi- loop to the corrin ring also has been cursor of vitamin B . well established (12). However, despite noglycan or able to accumulate this 12 all this research, little information was high-molecular-weight polymer. One of forthcoming on the synthesis of the the variants from their screen that accu- Conflict of interest statement: No conflicts declared. lower nucleotide base, DMB. mulated succinylgylcan was found to See companion article on page 4634 in issue 12 of volume The majority of early work on the be inactivated in a gene that displayed 103. synthesis of the DMB moiety of vitamin a high level of similarity to bluB, a gene *E-mail: [email protected]. B12 was based on studies with the obli- previously identified as causing a vita- © 2006 by The National Academy of Sciences of the USA www.pnas.org͞cgi͞doi͞10.1073͞pnas.0601030103 PNAS ͉ March 28, 2006 ͉ vol. 103 ͉ no. 13 ͉ 4799–4800 Downloaded by guest on September 27, 2021 Fig. 1. Transformation of FMN into DMB and its subsequent incorporation into vitamin B12. The portion of FMN that is transformed into DMB is highlighted in blue. This transformation is likely to require BluB and molecular oxygen. The incorporation of DMB into vitamin B12 requires the actions of three enzymes, CobT, C, and S. Although the evidence is very strong biochemical proof is required to demon- process suggests a retro-aldol condensa- in supporting a role for BluB in the bio- strate that it catalyzes a reaction associ- tion sandwiched between two 2-electron synthesis of DMB, a note of caution has ated with DMB formation. Because oxidations (13, 16). This number of to be added. It had been suggested that BluB belongs to the NADH͞FMN oxi- steps seems too much to be catalyzed by CobT (NaMN:DMB phosphoribosyl- doreductase family, it is plausible that it a single (small, 15-kDa) enzyme. So are transferase) synthesized DMB (21), could catalyze the oxygenation of FMN, other enzymes involved, such as the poign- although this hypothesis was subse- a prerequisite to the fragmentation of antly named bluF gene (23)? And what quently shown not to be the case. More- the flavin. The abiotic conversion of does BluB actually do? Moreover, some over, within the B12 pathway, mutational FMN to DMB has been shown (16, 17), organisms such as Salmonella enterica inactivation of one gene sometimes can although, contrary to the suggestion in also make DMB from FMN but do not apparently affect other parts of the Campbell et al. (1), it was never claimed appear to have a bluB orthologue, so pathway. So, for instance, the activity of that that this abiotic process is the phys- how do they catalyze this reaction? CbiD (a methyltransferase) requires the iological source of DMB. Moreover, it is These are the really interesting ques- presence of the amidases CbiA and P not clear whether the transformation of tions that need to be addressed next as (22). Thus, to confirm truly the role of FMN into DMB will require one or sev- the enigmatic and furtive biosynthesis of BluB in the biosynthesis of DMB, direct eral steps (Fig. 1). The chemistry of the cobalamin is further unraveled. 1. Campbell, G. R. O., Taga, M. E., Mistry, K., Lloret, 8. Scott, A. I. (1994) J. Nat. Prod. 57, 557–573. 16. Maggio-Hall, L. A., Dorrestein, P. C., Escalante- J., Anderson, P. J., Roth, J. R. & Walker, G. C. 9. Debussche, L., Thibaut, D., Cameron, B., Crouzet, Semerena, J. C. & Begley, T. P. (2003) Org. Lett. (2006) Proc. Natl. Acad. Sci. USA 103, 4634–4639. J. & Blanche, F. (1993) J. Bacteriol. 175, 7430– 5, 2211–2213. 2. Minot, G. R. & Murphy, W. P. (1926) J. Am. Med. 7440. 17. Renz, P., Wurm, R. & Horig, J. (1977) Z. Naturfor- Assoc. 87, 470. 10. Battersby, A. R. (1994) Science 264, 1551–1557. sch. C 32, 523–527. 3. Rickes, E. L, Brink, N. G., Koniuszy, F. R., Wood, 11. Blanche, F., Thibaut, D., Debussche, L., Hertle, 18. Pollich, M. & Klug, G. (1995) J.
Load more

Recommended publications
  • Anoxygenic Photosynthesis in Photolithotrophic Sulfur Bacteria and Their Role in Detoxication of Hydrogen Sulfide
    antioxidants Review Anoxygenic Photosynthesis in Photolithotrophic Sulfur Bacteria and Their Role in Detoxication of Hydrogen Sulfide Ivan Kushkevych 1,* , Veronika Bosáková 1,2 , Monika Vítˇezová 1 and Simon K.-M. R. Rittmann 3,* 1 Department of Experimental Biology, Faculty of Science, Masaryk University, 62500 Brno, Czech Republic; [email protected] (V.B.); [email protected] (M.V.) 2 Department of Biology, Faculty of Medicine, Masaryk University, 62500 Brno, Czech Republic 3 Archaea Physiology & Biotechnology Group, Department of Functional and Evolutionary Ecology, Universität Wien, 1090 Vienna, Austria * Correspondence: [email protected] (I.K.); [email protected] (S.K.-M.R.R.); Tel.: +420-549-495-315 (I.K.); +431-427-776-513 (S.K.-M.R.R.) Abstract: Hydrogen sulfide is a toxic compound that can affect various groups of water microorgan- isms. Photolithotrophic sulfur bacteria including Chromatiaceae and Chlorobiaceae are able to convert inorganic substrate (hydrogen sulfide and carbon dioxide) into organic matter deriving energy from photosynthesis. This process takes place in the absence of molecular oxygen and is referred to as anoxygenic photosynthesis, in which exogenous electron donors are needed. These donors may be reduced sulfur compounds such as hydrogen sulfide. This paper deals with the description of this metabolic process, representatives of the above-mentioned families, and discusses the possibility using anoxygenic phototrophic microorganisms for the detoxification of toxic hydrogen sulfide. Moreover, their general characteristics, morphology, metabolism, and taxonomy are described as Citation: Kushkevych, I.; Bosáková, well as the conditions for isolation and cultivation of these microorganisms will be presented. V.; Vítˇezová,M.; Rittmann, S.K.-M.R.
    [Show full text]
  • Myoglobin with Modified Tetrapyrrole Chromophores: Binding Specificity and Photochemistry ⁎ Stephanie Pröll A, Brigitte Wilhelm A, Bruno Robert B, Hugo Scheer A
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Biochimica et Biophysica Acta 1757 (2006) 750–763 www.elsevier.com/locate/bbabio Myoglobin with modified tetrapyrrole chromophores: Binding specificity and photochemistry ⁎ Stephanie Pröll a, Brigitte Wilhelm a, Bruno Robert b, Hugo Scheer a, a Department Biologie I-Botanik, Universität München, Menzingerstr, 67, 80638 München, Germany b Sections de Biophysique des Protéines et des Membranes, DBCM/CEA et URA CNRS 2096, C.E. Saclay, 91191 Gif (Yvette), France Received 2 August 2005; received in revised form 2 March 2006; accepted 28 March 2006 Available online 12 May 2006 Abstract Complexes were prepared of horse heart myoglobin with derivatives of (bacterio)chlorophylls and the linear tetrapyrrole, phycocyanobilin. Structural factors important for binding are (i) the presence of a central metal with open ligation site, which even induces binding of phycocyanobilin, and (ii) the absence of the hydrophobic esterifying alcohol, phytol. Binding is further modulated by the stereochemistry at the isocyclic ring. The binding pocket can act as a reaction chamber: with enolizable substrates, apo-myoglobin acts as a 132-epimerase converting, e.g., Zn-pheophorbide a' (132S) to a (132R). Light-induced reduction and oxidation of the bound pigments are accelerated as compared to solution. Some flexibility of the myoglobin is required for these reactions to occur; a nucleophile is required near the chromophores for photoreduction (Krasnovskii reaction), and oxygen for photooxidation. Oxidation of the bacteriochlorin in the complex and in aqueous solution continues in the dark. © 2006 Elsevier B.V.
    [Show full text]
  • Biofilm Forming Purple Sulfur Bacteria Enrichment from Trunk River
    Different biofilm-forming purple sulfur bacteria enriched from Trunk River Xiaolei Liu Abstract Three different types of biofilm were developed on the bottles of purple sulfur bacteria enrichments. The original inoculum is a piece of sea grass covered with purple biofilm that collected from Trunk River during the course. Microscopy imaging showed that two of the three biofilms were apparently composed of two major species. MonoFISH probing supports the recognition of purple sulfur bacteria as Chromatium in the class of gammaproteobacteria which grow together with a deltaproteobacteria species. Such a combination of Chromatium colonize with deltaproteobacteria species is also originally present in the purple biofilm on sea grass. Further work is needed to investigate the potential interactions between these two species. Introduction Purple sulfur bacteria are photosynthetic anearobes in the phylum of Proteobacteria (Fowler et al., 1984), which is capable of fixing carbon dioxide with sulfide other than water as the electron donors. Since oxygen is not produced during their photosynthesis these purple sulfur bacteria are also known as anoxygenic photoautotrophs. Most purple sulfur bacteria synthesize bacteriochlorophyll and carotenoids as their light-harvesting pigment complex (Iba et al., 1988). Because their photosynthesis reQuires anoxic condition and sulfide, these purple sulfur bacteria are often found in organic rich aquatic environments where sulfate reducing heterotrophic bacteria thrive. Both planktonic and benthic species of purple sulfur bacteria exist in different sulfidic environments. In the habitat of stratified meromictic lakes with external sulfate input, such as Green Lake, Mahoney Lake and Lake Cadagno, the phototrophic chemocline microbial communities are often dominated by planktonic purple sulfur bacteria living on sulfide diffused up from organic rich sediment (e.g.
    [Show full text]
  • Structure of the Biliverdin Radical Intermediate in Phycocyanobilin
    Published on Web 01/21/2009 Structure of the Biliverdin Radical Intermediate in Phycocyanobilin:Ferredoxin Oxidoreductase Identified by High-Field EPR and DFT Stefan Stoll,*,† Alexander Gunn,† Marcin Brynda,†,| Wesley Sughrue,†,‡ Amanda C. Kohler,‡,⊥ Andrew Ozarowski,§ Andrew J. Fisher,†,‡ J. Clark Lagarias,‡ and R. David Britt*,† Department of Chemistry and Section of Molecular and Cellular Biology, UniVersity of California DaVis, 1 Shields AVenue, DaVis, California 95616, and National High Magnetic Field Laboratory, Florida State UniVersity, 1800 East Paul Dirac DriVe, Tallahassee, Florida 32310 Received October 31, 2008; E-mail: [email protected] (S.S.); [email protected] (R.D.B.) The cyanobacterial enzyme phycocyanobilin:ferredoxin oxidoreductase (PcyA) catalyzes the two- step four-electron reduction of biliverdin IXR to phycocyanobilin, the precursor of biliprotein chromophores found in phycobilisomes. It is known that catalysis proceeds via paramagnetic radical intermediates, but the structure of these intermediates and the transfer pathways for the four protons involved are not known. In this study, high-field electron paramagnetic resonance (EPR) spectroscopy of frozen solutions and single crystals of the one-electron reduced protein-substrate complex of two PcyA mutants D105N from the cyanobacteria Synechocystis sp. PCC6803 and Nostoc sp. PCC7120 are examined. Detailed analysis of Synechocystis D105N mutant spectra at 130 and 406 GHz reveals a biliverdin radical with a very narrow g tensor with principal values 2.00359(5), 2.00341(5), and 2.00218(5). Using density-functional theory (DFT) computations to explore the possible protonation states of the biliverdin radical, it is shown that this g tensor is consistent with a biliverdin radical where the carbonyl oxygen atoms on both the A and the D pyrroleringsareprotonated.Thisexperimentallconfirmsthereactionmechanismrecentlyproposed(Tu, et al.
    [Show full text]
  • Bacteriochlorophyll Biosynthesis in Rhodopseudomonas Capsulata in Response to Oxygen
    JOURNAL OF BACTERIOLOGY, Nov. 1983, p. 686-694 Vol. 156, No. 2 0021-9193/83/110686-09$02.00/0 Copyright © 1983, American Society for Microbiology Transcriptional Regulation of Several Genes for Bacteriochlorophyll Biosynthesis in Rhodopseudomonas capsulata in Response to Oxygen ALAN J. BIELt AND BARRY L. MARRSt* E. A. Doisy Department ofBiochemistry, Saint Louis University School of Medicine, St. Louis, Missouri 63104 Received 27 June 1983/Accepted 23 August 1983 Although it has been shown that bacteriochlorophyll synthesis in Rhodopseudo- monas capsulata is repressed by oxygen and high light intensity, few details of regulation by these environmental factors are known, primarily owing to a lack of assays for the biosynthetic enzymes. We have examined regulation at the transcriptional level by isolating and studying fusions between the Mu dl(Apr lac) phage and various bch genes. In these strains, the lacZ gene of the phage is under the control of bch gene promoters. We have found that atmospheric oxygen tension (20% 02) reduces the expression of these fusions at least twofold compared with low oxygen tension (2% 02). Therefore, transcription of the bchA, bchB, bchC, bchG, and bchH genes is regulated in response to oxygen. In Rhodopseudomonas capsulata, the biosyn- by whole-cell suspensions of Rhodopseudo- thesis of protoheme and bacteriochlorophyll fol- monas spheroides. This conversion only oc- lows a common pathway from the condensation curred when the cells were grown under low of succinyl coenzyme A with glycine to the oxygen tension. However, further work was formation of protoporphyrin IX. Biosynthesis of hampered by the inability of cell extracts to protoheme and bacteriochlorophyll proceeds catalyze the chelation of magnesium.
    [Show full text]
  • Picoplankton Distribution and Activity in the Deep Waters of the Southern Adriatic Sea
    water Article Picoplankton Distribution and Activity in the Deep Waters of the Southern Adriatic Sea Danijela Šanti´c 1,* , Vedrana Kovaˇcevi´c 2, Manuel Bensi 2, Michele Giani 2 , Ana Vrdoljak Tomaš 1 , Marin Ordulj 3 , Chiara Santinelli 2, Stefanija Šestanovi´c 1, Mladen Šoli´c 1 and Branka Grbec 1 1 Institute of Oceanography and Fisheries, Šetalište Ivana Meštrovi´ca63, POB 500, 21000 Split, Croatia 2 National Institute of Oceanography and Applied Geophysics, Borgo Grotta Gigante 42/c, 34010 Sgonico (Ts), Italy 3 University of Split, University Department of Marine Studies, Ruđera Boškovi´ca37, 21000 Split, Croatia * Correspondence: [email protected]; Tel.: +385-21-408-006; Fax: +385-21-358-650 Received: 19 July 2019; Accepted: 8 August 2019; Published: 10 August 2019 Abstract: Southern Adriatic (Eastern Mediterranean Sea) is a region strongly dominated by large-scale oceanographic processes and local open-ocean dense water formation. In this study, picoplankton biomass, distribution, and activity were examined during two oceanographic cruises and analyzed in relation to environmental parameters and hydrographic conditions comparing pre and post-winter phases (December 2015, April 2016). Picoplankton density with the domination of autotrophic biomasses was higher in the pre-winter phase when significant amounts of picoaoutotrophs were also found in the meso-and bathy-pelagic layers, while Synechococcus dominated the picoautotrophic group. Higher values of bacterial production and domination of High Nucleic Acid content bacteria (HNA bacteria) were found in deep waters, especially during the post-winter phase, suggesting that bacteria can have an active role in the deep-sea environment. Aerobic anoxygenic phototrophic bacteria accounted for a small proportion of total heterotrophic bacteria but contributed up to 4% of bacterial carbon content.
    [Show full text]
  • Purification and Characterization of Rhodobacter Sphaeroides Polyhistidine-Tagged Hema and Comparison with Purified Polyhistidine- Tagged Hemt
    PURIFICATION AND CHARACTERIZATION OF RHODOBACTER SPHAEROIDES POLYHISTIDINE-TAGGED HEMA AND COMPARISON WITH PURIFIED POLYHISTIDINE- TAGGED HEMT Xiao Xiao A Thesis Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 2013 Committee: Dr. Jill Zeilstra-Ryalls, Ph.D., Advisor Dr. Rogers O. Scott Dr. Zhaohui Xu ii © 2013 Xiao Xiao All Rights Reserved iii ABSTRACT Jill Zeilstra-Ryalls, Ph.D, Advisor All tetrapyrrole, molecules that include heme, bacteriochlorophyll, and vitamin B12, are derived from 5-aminolevulinic acid (ALA). In the purple non-sulfur alphaproteobacteria Rhodobacter sphaeroides ALA is formed by the condensation of glycine and succinyl-CoA, catalyzed by the pyridoxal-phosphate dependent enzyme ALA synthase. Two ALA synthase genes, hemA and hemT are present in R. sphaeroides wild type strain 2.4.1. When expressed, either one of the gene products can satisfy the ALA requirement of the cell. Towards understanding the presence of two ALA synthases in one organism, each enzyme should be characterized individually in order to define what is similar and different about the enzymes. Using this information, one may be able to infer how the activities of the two ALA synthases are coordinate in R. sphaeroides. In this study, R. sphaeroides 2.4.1 recombinant polyhistidine- tagged HemA (rHemA) was affinity purified and its optimum temperature and pH, specific activity, and kinetic properties were determined. The effect of added hemin on its activity was also evaluated, as was its secondary structure composition using circular dichroism. These characteristics were then compared to those of recombinant polyhistidine-tagged HemT (rHemT).
    [Show full text]
  • Hemin and Chlorophyll— the Two Most Important Pigments for Life on Earth1
    THE OHIO JOURNAL OF SCIENCE VOL. LVI JULY, 1956 No. 4 HEMIN AND CHLOROPHYLL— THE TWO MOST IMPORTANT PIGMENTS FOR LIFE ON EARTH1 PAUL ROTHEMUND The Ohio State University, Columbus, 10, and Muskingum College, New Concord, Ohio Two chemical processes are the prerequisites for all life on earth: the absorption of some of the energy from the sun in the green plants and its transformation into carbon compounds on one hand, and the use of the chemical energy of these compounds by animals in controlled decomposition reactions on the other. From the chemist's point of view the green leaf is a veritable chemical labora- tory: carbon dioxide from the air, and water and inorganic salts from the soil are the raw material, the visible portion of the sun radiation furnishes the energy, and the numerous complex constituents of the plant represent the manufactured products. Some of the substances synthesized are structural matter, like cellulose in the wood, or cork in the bark, others are food reserves, as starch in the grains of corn or wheat, or in potatoes. Of the many other materials produced in the green plant only a few may be enumerated here, sugars, fats, oils and waxes, proteins and nucleic acids, fibers like cotton or hemp, vitamins, hormones, indigo and other dyes, latex for producing rubber, alkaloids like the nicotin in tobacco leaves, valuable medicinally used compounds, such as quinine, cocaine, and morphine, and—most important—the green pigment chlorophyll. "Photo- synthesis", or the "assimilation of carbon dioxide" is the biochemical process, in which simply constructed and relatively inert inorganic compounds are built up into the highly complex, reactive and sensitive organic compounds, which characterize living matter.
    [Show full text]
  • And Formation
    J Med Genet: first published as 10.1136/jmg.17.1.1 on 1 February 1980. Downloaded from Review article Journal of Medical Genetics, 1980, 17, 1-14 Haems and chlorophylls: comparison of function and formation G A F HENDRY AND 0 T G JONES From the Department ofBiochemistry, The Medical School, University ofBristol, Bristol BS8 ITD In 1844 Verdeill reported that acid treatment of at the same time by McMunn3 of cytochromes, chlorophyll or haem yielded apparently similar red another group of haem proteins. compounds; he even postulated that chlorophylls It was the demonstration by Nencki and co- would contain iron. Hoppe-Seyler2 confirmed the workers 45 that the degradation of both chlorophylls apparent similarity of acid derivatives of haems and and haems yielded monopyrroles that led them, in chlorophylls from their light absorption charac- true neo-Darwinian fashion, to postulate a common teristics, a point rather overshadowing the discovery origin for animals and plants. 0 0-'I CH2 II copyright. CH CH3 COOH CIH2 CH2 C-O CH2 http://jmg.bmj.com/ NH2 ( CH3' 'CH3 ® 5- Aminolaevulinic acid a CH2 2 1 12 2 CH2 )H COOH CD FIG 1 Structures ofprotohaem and Protoporphyrin IX chlorophyll a and two of their precursors, acid and 5-aminolaevulinic on September 30, 2021 by guest. Protected protoporphyrin IX (with substituent numbering positions). CH2 CH CH.--,j CH2 CH2 COOCH3 Protohoem (haem- b) CooC20H39 Chlorophyll a 1 J Med Genet: first published as 10.1136/jmg.17.1.1 on 1 February 1980. Downloaded from 2 G A F Hendry and 0 T G Jones Following the work ofWillstatter6 and Fischer and particularly those of avian egg shells, have no Stern,7 the structure of most natural and many central complexed metal.
    [Show full text]
  • ROBERT HUBER Max-Planck-Institut Für Biochemie, 8033 Martinsried
    A STRUCTURAL BASIS OF LIGHT ENERGY AND ELECTRON TRANSFER IN BIOLOGY Nobel Lecture, December 8, 1988 by ROBERT HUBER Max-Planck-Institut für Biochemie, 8033 Martinsried Dedicated to Christa ABBREVIATIONS PBS, phycobilisomes; light harvesting organelles peripheral to the thylakoid membrane in cyanobacteria, which carry out oxygenic photosynthesis and have photosystems I and II; PE, PEC, PC, APC, phycoerythrin, phycoerythrocyanin, phycocyanin, allo- phycocyanin; biliprotein components in PBS with covalently attached tetra- pyrrole (bilin) pigments; PS I, II; photosynthetic reaction centers in chloroplasts and cyanobacteria; EBP; retinol binding protein; BBP, bilin (biliverdin IX); binding protein in Pieris brassicae; A Rps. viridis, bacteriochlorophyll-b containing purple bacterium carrying out anoxygenic photosynthesis; RC, reaction centre; C, H, L, M; the four subunits of the reaction centre from Rps. viridis: the cytochrome c subunit (C), with 4 haems displaying two redox potentials is located on the periplasmic side of the membrane; the L- and M- subunits are integrated in the membrane and their polypeptide chains span the membrane with 5 each, labelled A, B, C, D, E; they bind the bacteriochlorophyll-b (BChl-b or BC), bacteriopheophytin-b (BPh-b or BP), 2+ menaquinone-9 (Q A), ubiquinone-9 (UQ,Q B) and Fe cofactors; the sub- scripts P, A, M, L indicate pair, accessory, M-, L-subunit association, respec- tively; the H-subunit is located on the cytoplasmic side and its N-terminal α− helical segment (H) spans the membrane; P680, P960; primary electron donors in PS II and the RC of Rps. viridis, respectively, indicating the long wavelength absorption maxima; electronically excited states of P and D A; LHC, light harvesting complexes; light harvesting protein pigment complexes in BChl-a,b containing bacteria; R.
    [Show full text]
  • In Situ Formation of Photoactive B-Ring Reduced Chlorophyll Isomer In
    www.nature.com/scientificreports OPEN In situ formation of photoactive B‑ring reduced chlorophyll isomer in photosynthetic protein LH2 Yoshitaka Saga1*, Yuji Otsuka1, Daichi Funakoshi2, Yuto Masaoka2, Yu Kihara2, Tsubasa Hidaka2, Hiroka Hatano3, Hitoshi Asakawa3,4, Yutaka Nagasawa2 & Hitoshi Tamiaki2 Natural chlorophylls have a D‑ring reduced chlorin π‑system; however, no naturally occurring photosynthetically active B‑ring reduced chlorins have been reported. Here we report a B‑ring reduced chlorin, 17,18‑didehydro‑bacteriochlorophyll (BChl) a, produced by in situ oxidation of B800 bacteriochlorophyll (BChl) a in a light‑harvesting protein LH2 from a purple photosynthetic bacterium Phaeospirillum molischianum. The regioselective oxidation of the B‑ring of B800 BChl a is rationalized by its molecular orientation in the protein matrix. The formation of 17,18‑didehydro‑BChl a produced no change in the local structures and circular arrangement of the LH2 protein. The B‑ring reduced 17,18‑didehydro‑BChl a functions as an energy donor in the LH2 protein. The photoactive B‑ring reduced Chl isomer in LH2 will be helpful for understanding the photofunction and evolution of photosynthetic cyclic tetrapyrrole pigments. Cyclic tetrapyrroles with modifed skeletons and peripheral groups have essential roles in various biofunctional proteins1–3. Chlorophyll (Chl) molecules, involved in the solar-energy conversion processes of oxygenic photo- synthesis, typically contain an unsymmetrical conjugated tetrapyrrole π-system, in which the C17–C18 bond in the D-ring is hydrogenated 1,4–8. Te D-ring reduced chlorin (17,18-dihydroporphyrin) skeleton is responsible for efcient light absorption in the visible portion of the solar spectrum.
    [Show full text]
  • Discovery of Zinc-Bacteriochlorophyll in Rhodobacter Sphaeroides Paul R
    Discovery of zinc-bacteriochlorophyll in Rhodobacter sphaeroides Paul R. Jaschke and J.Thomas Beatty Department of Microbiology and Immunology, University of British Columbia Introduction Results Conclusions At the heart of photosynthesis are the chlorophyll pigments This work shows that in a cell previously thought to be devoid of any responsible for absorption and transmission of light energy. How the of any photosynthetic pigments (3), there are small quantities of Zn- How the cell synthesizes and distributes these pigments to the Zn-BChl that assemble into the RC complex. Although never seen photosynthetic apparatus (Fig 1) of Rhodobacter sphaeroides (Fig 2) 1. BChl is absent in bchD mutant but a pigment 2. Identification of Zn-BChl. seen before in R. sphaeroides, such a Zn-BChl pigment was initially 2) is the focus of this study. with similar spectral properties is present. To further characterize this pigment we used MALDI-TOF mass spectrometry initially discovered in Acidiphilium rubrum where it is used as a spectrometry on the isolated sample. The major molecular ion peak (M+) was photosynthetic pigment in the RC (6, 8). We have yet to assess Outer Membrane To determine whether the bchD mutant made any photosynthetic pigments, cell functionality of R. sphaeroides’ Zn-BChl RC but it is presumed that Figure 1. pigments, cell extractions were ran on HPLC (Fig 5A). BChl was conspicuously (M+) was 950.6 m/z, which agrees well with the predicted mass of Zn-BChl Cytochrome c2 + - hv BChl (M+=950.4), but not with any other metal BChl derivative (Fig 6A). that without BPhe there will be incomplete electron flow and no H e Photosynthetic energy conspicuously absent from these cells, but a major peak not seen in wild type Periplasm Upon treatment with acid, which is known to demetallate BChl, another peak at no reduction of the quinones, rendering this RC non-functional.
    [Show full text]