DOCSLIB.ORG

Photophosphorylation in Halobacterium Halobium

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Photophosphorylation in Halobacterium Halobium Proc. Nat. Acad. Sci. USA Vol. 71, No. 4, pp. 1234-1238, April 1974 Photophosphorylation in Halobacterium halobium (Halobacteria/photosynthesis/bacteriorhodopsin/chemiosmotic theory/active transport) ARLETTE DANON* AND WALTHER STOECKENIUSt * The Weizmann Institute of Science, Rehovot, Israel; and t Cardiovascular Research Institute and Department of Biochemistry and Biophysics, University of California, San Francisco, Calif. 94143 Communicated by Daniel I. Arnon, November 14, 1973 ABSTRACT Halobacterium halobium cells grown un- We show here that apparently purple membrane-containing der semi-anaerobic conditions convert part of their cell H. halobium cells are capable of photophosphorylation using a membrane into "purple membrane" which contains a which is different in its first energy conversion rhodopsin-like protein, bacteriorhodopsin. Under anaero- mechanism bic conditions in the dark the ATP content of such cells steps from that used by chlorophyll-containing organisms. decreases sharply. Either light or oxygen restores the ATP MATERIALS AND METHODS content to the original level. The light effect is mediated by the purple membrane. Inhibitors of the respiratory Cell Strain and Growth Conditions. For all experiments chain abolish the oxygen response but do not affect the Halobacterium halobium R, was used (5). Cells were grown at light response. Uncouplers, which function as proton on a gyratory shaker in a synthetic medium (6) supple- translocators, abolish the light response. These results in- 370 dicate that the purple membrane functions as a light- mented with 2% malate. The amount of purple membrane driven proton pump and the cells use the resulting chemi- formed depends on illumination (7, 8, 3). Illumination was osmotic gradient for ATP synthesis. provided by cool white fluorescent lamps and kept constant at 5 to 6 X 104 ergs/cm2 per sec. Aeration was controlled by The extreme halophile Halobacterium halobium, when grown varying the amount of growth medium in the culture vessels. at low 02 concentrations in the light, synthesizes a rhodop- At a medium to vessel volume ratio of 1:15, the formation of sin-like protein-bacteriorhodopsin-which forms distinct the purple membrane was suppressed; at the ratio of 1:2, patches in the surface membrane of the cell and may occupy optimal purple membrane yields were obtained. The cultures about 50% of the total membrane area (1-3). Bacteriorho- a cell density of about 108 cells per ml and nm were inoculated at dopsin has a broad absorption maximum around 560 grown until the cell density of 6 to 10 X 108 had been reached. which lends a deep purple' color to the isolated membrane patches. The patches have been termed tlih purple membrane. Analytical Techniques. Purple membrane content of the Bacteriorhodopsin is the' only protein found in the purple cells was determined on 40-ml aliquots of the culture. Cells membrane which, in addition, contains only 25% lipids. were harvested by centrifugation and lysed by dialysis against When the purple membrane is exposed to a flash of visible distilled water (5). The lysate was centrifuged at 50,000 X g light, the absorption maximum shifts to 415 nm with a fast for 30 min and the pellet resuspended in 2-5 ml of distilled return to the long wavelength form in the dark (Cone, R. A., water; any remaining turbidity was removed by centrifuga- Fein, A., and Stoeckenius, W., unpublished). This transient tion at 700 X g for 5 min. To one-half of the sample 0.1 M bleaching is accompanied by a cyclic release and uptake of cetyltrimethylammonium bromide (CTAB) pH 8.0 was added protons. Under continuous illumination the pigment ap- to give a final concentration of 0.01 M; this shifts the purple parently oscillates rapidly between the long and short wave- membrane absorption maximum to 369 nm (1). The difference length form and, when it is incorporated into the surface spectrum between the CTAB-treated and the untreated membrane of the cell, the concomitant release and uptake of sample was obtained on a Cary 14 spectrophotormeter protons occurs as a vectorial reaction, resulting in a net out- equipped with the accessory for scattering samples. The purple ward translocation of protons from the cells (3). The resultant membrane concentration is expressed as AOD 570 nm/mg of electrochemical gradient can presumably be used to satisfy cell protein. Protein was determined by the Lowry technique. the energy requirements of the cell according to Mitchell's ATP was determined in 0.2-ml samples of the cell suspen- chemiosmotic theory for energy coupling (4). sion, which were rapidly diluted into 1.8 ml of 0.02 M boiling Tris - HCl buffer (pH 7.4 at room temperature). Boiling was continued for an additional 5 min, and the sample cooled in ice. The luciferin-luciferase assay was used according to ATP concentrations Abbreviations: ATPase, adenosine triphosphatase; dC'CP, keto- Stanley and Williams (9). Negligible malononitrile 3-chlorophenylhydrazone(carbonylcyanide 3-chlo- were found in the suspension medium after separation from rophenylhydrazone); QTAB, cetyltrimethylammonium bromide; the cells. DCCD, N,N'-dicyclohexylcarbodiimide; DCMU, 3-(3,4-dichlo- Assay Conditions. Cells were harvested by centrifugation rophenyl)-1,1-dimethylurea; DNP, 2-dinitrophenol; FCCP, and resuspended to an OD of 0.5 at 640 nm in a salt solution ketomalononitrile 4-trifluoromethoxyphenylhydrazone(carbonyl- but without the nutrients. 4-trifiuoromethoxyphenylhydrazone); NQNO, 2-n-nonyl- identical to the growth medium cyanide The cells were kept under aeration for at least 2 hr at 370 be- 4-hydroxyquinoline-N-oxide; PMS, N-methylphenazonium This methosulfate (phenazine methosulfate). fore 20-ml samples were transferred to the assay vessel. 1234 Proc. Nat. Acad. Sci. USA 71 (1974) Photophosphorylation in Halobacterium halobium 1235 OA_ 570 N2 N2 02 I 11l w A B 12 0 02_ b a a 0 0. 6mMM 011;* -- a 4 KCN 0~~~~KC 0 10- I~~ I I -0.2 -V , As _ _. _ _ 4 5 369 5 '10' 60 80 1O 60 80 350 450 550 Minutes nm FIG. 1. Difference spectrum of unbleached minus CTAB- FIG. 3. Effect of an electron transport inhibitor on the light bleached membrane preparation of vigorously aerated (a) and (A) and 02 (B) response of cells. Only the 02 response is affected. poorly aerated cells (b). The maximum at 570 nm and minimum ATP per mg of protein at time 0 = 15.6 nmol. AOD 570 nm/mg at 369 nm, which are characteristic for the purple membrane, are of protein = 0.101. present only in the preparation from poorly aerated cells. RESULTS magnetically stirred glass vessel had a capacity of 50 ml and Fig. 1 shows an example of the difference spectra used for was surrounded by a water bath kept at 37°. For some experi- determination of purple membrane content of the cells. It ments it was equipped with a pH electrode. Provisions for should, however, be noted that the total amount of material bubbling the cell suspension with N2 or 02 and for the removal in the preparations from cells containing little purple mem- of samples were made. In some experiments cells were sparged brane is small because the centrifugation at 50,000 X g for 30 with N2 in a larger vessel and then transferred anaerobically min will almost exclusively sediment the purple membrane to the assay vessel flushed with N2. from the cell lysate and most of the other surface membrane Light sources were either a 250-W flood lamp or a 500-W fragments-the red membrane (5, 10)-remain in suspension. tungsten filament lamp in a slide projector. Balzers broad- Samples from cells containing high concentrations of purple band and narrow-band filters (Filtraflex K 1-7 and B10) were membrane therefore scatter considerably more light, and the used. A 5-cm thick flat-sided flask filled with water and cooled OD measured becomes dependent on the geometry of the spec- by a fan served as a heat filter. Light intensity was measured trophotometer used. Differences in scattering between CTAB- with a Yellow Springs light meter (YSI model 65). treated and untreated reference also become significant. Nevertheless, the technique may be used for a rough com- parison of the amount of purple membrane in the cultures, provided the same spectrophotometer is used in all experi- ments and care is taken to minimize the effects due to dif- ferences in light scattering. The highest values of AOD 570 nm/mg of protein for cells grown at low PO2 as described under Methods are about 0.4. At this concentration, a large part of the cell surface membrane consists of purple membrane (3). The chilling and centrifugation during harvesting sharply reduces the ATP content of cells. The loss is recovered when N2 02 120 B 80 -h-v IC - ~~~~~~~~~~~~~~~I 4e 0 40 -0~~~~~0 - +h-v 0 20 40 60 80 Minutes FIG. 2. Cells incubated in the dark under N2 show a fast drop in ATP content. Only the poorly aerated cells, which contain purple membrane, respond to light (h.av) with an increase of Minutes ATP content (A). Both vigorously aerated (B) and poorly aerated FIG. 4. Effect of phenazine methosulfate (PMS) on the 02 and cells (A) increase their ATP content when 02 is admitted. ATP light response of cells. Only the 02 response is affected. ATP per per mg of protein at time 0: (A) 14.4 nmol; (B) 14.9 nmol. AOD mg of protein at time 0 = 32.5 nmol. AOD 570 nm/mg of protein 570 nm/mg of protein: (A) 0.155; (B) 0.009. = 0.208. 1236 Cell Biology: Danon and Stoeckenius Proc. Nat. Acad. Sci. USA 71 (1974) TABLE 1. Effects ofinhibitors on ATP increase in N2 H.
Load more

Recommended publications
  • Light-Induced Psba Translation in Plants Is Triggered by Photosystem II Damage Via an Assembly-Linked Autoregulatory Circuit
    Light-induced psbA translation in plants is triggered by photosystem II damage via an assembly-linked autoregulatory circuit Prakitchai Chotewutmontria and Alice Barkana,1 aInstitute of Molecular Biology, University of Oregon, Eugene, OR 97403 Edited by Krishna K. Niyogi, University of California, Berkeley, CA, and approved July 22, 2020 (received for review April 26, 2020) The D1 reaction center protein of photosystem II (PSII) is subject to mRNA to provide D1 for PSII repair remain obscure (13, 14). light-induced damage. Degradation of damaged D1 and its re- The consensus view in recent years has been that psbA transla- placement by nascent D1 are at the heart of a PSII repair cycle, tion for PSII repair is regulated at the elongation step (7, 15–17), without which photosynthesis is inhibited. In mature plant chloro- a view that arises primarily from experiments with the green alga plasts, light stimulates the recruitment of ribosomes specifically to Chlamydomonas reinhardtii (Chlamydomonas) (18). However, we psbA mRNA to provide nascent D1 for PSII repair and also triggers showed recently that regulated translation initiation makes a a global increase in translation elongation rate. The light-induced large contribution in plants (19). These experiments used ribo- signals that initiate these responses are unclear. We present action some profiling (ribo-seq) to monitor ribosome occupancy on spectrum and genetic data indicating that the light-induced re- cruitment of ribosomes to psbA mRNA is triggered by D1 photo- chloroplast open reading frames (ORFs) in maize and Arabi- damage, whereas the global stimulation of translation elongation dopsis upon shifting seedlings harboring mature chloroplasts is triggered by photosynthetic electron transport.
    [Show full text]
  • Photosynthetic Phosphorylation Above and Below 00C by David 0
    VOL. 48, 1962 BIOCHEMISTRY: HALL AND ARNON 833 10 De Robertis, E., J. Biophy8. Biochem. Cytol., 2, 319 (1956). 11 Eakin, R. M., and J. A. Westfall, ibid., 8, 483 (1960). 12 Eakin, R. M., these PROCEEDINGS, 47, 1084 (1961). 13 Wolken, J. J., in The Structure of the Eye, ed. G. K. Smelser (New York: Academic Press, 1961). 14 Wald, G., ibid. 16 Eakin, R. M., and J. A. Westfall, Embryologia, 6, 84 (1961). 16 Sj6strand, F. S., in The Structure of the Eye, ed. G. K. Smelser (New York: Academic Press, 1961). 17 Miller, W. H., in The Cell, ed. J. Brachet and A. E. Mirsky (New York: Academic Press, 1960), part IV. 18 Miller, W. H., J. Biophys. Biochem. Cytol., 4, 227 (1958). 19 Hesse, R., Z. wiss. Zool., 61, 393 (1896). 20 Bradke, D. L., personal communication. 21 Wolken, J. J., Ann. N. Y. Acad. Sci., 74, 164 (1958). 22 Rohlich, P., and L. J. Torok, Z. wiss. Zool., 54, 362 (1961). 28 Eakin, R. M., and J. A. Westfall, J. Ultrastr. Res. (in press). 24 Franz, V., Jena. Z. Naturwiss., 59, 401 (1923). PHOTOSYNTHETIC PHOSPHORYLATION ABOVE AND BELOW 00C BY DAVID 0. HALL* AND DANIEL I. ARNONt DEPARTMENT OF CELL PHYSIOLOGY, UNIVERSITY OF CALIFORNIA, BERKELEY Read before the Academy, April 25, 1962 CO2 assimilation in photosynthesis consists of a series of dark enzymatic reactions that are driven solely by adenosine triphosphate and reduced pyridine nucleotide. 1-4 The same reactions are now known to operate in nonphotosynthetic cells.5-"3 It follows, therefore, that the distinction between carbon assimilation in photosyn- thetic and nonphotosynthetic cells lies in the manner in which ATP14 and PNH214 are formed.
    [Show full text]
  • Bacterial Photophosphorylation: Regulation by Redox Balance* by Subir K
    VOL. 49, 1963 BIOCHEMISTRY: BOSE AND GEST 337 12 Hanson, L. A., and I. Berggird, Clin. Chim. Acta, 7, 828 (1962). 13 Stevenson, G. T., J. Clin. Invest., 41, 1190 (1962). 14 Burtin, P., L. Hartmann, R. Fauvert, and P. Grabar, Rev. franc. etudes clin. et biol., 1, 17 (1956). 15 Korngold, L., and R. Lipari, Cancer, 9, 262 (1956). 16Lowry, 0. H., N. J. Rosebrough, A. L. Farr, and R. J. Randall, J. Biol. Chem., 193, 265 (1951). 17 Muller-Eberhard, H. J., Scand. J. Clin. and Lab. Invest., 12, 33 (1960). 18 Bergg&rd, I., Arkiv Kemi, 18, 291 (1962). 19 BerggArd, I., Arkiv Kemi, 18, 315 (1962). 20 Flodin, P., Dextran Gels and Their Application in Gel Filtration (Uppsala: Pharmacia, 1962). 21 Dische, Z., and L. B. Shettles, J. Biol. Chem., 175, 595 (1948). 22 Kunkel, H. G., and R. Trautman, in Electrophoresis, ed. M. Bier (New York: Academic Press, 1959), p. 225. 23Fleischman, J. B., R. H. Pain, and R. R. Porter, Arch. Biochem. Biophys., Suppl. 1, 174 (1962). 24 Porter, R. R., Biochem. J., 73, 119 (1959). 25 Edelman, G. M., J. F. Heremans, M.-Th. Heremans, and H. G. Kunkel, J. Exptl. Med., 112, 203 (1960). 26 Scheidegger, J. J., Intern. Arch. Allergy Appl. Immunol., 7, 103 (1955). 27 Yphantis, D. A., American Chemical Society, 140th meeting, Chicago, Abstracts of Papers, 1961, p. ic. 28 Gally, J. A. and G. M. Edelman, Biochim. Biophys. Acta, 60, 499 (1962). 29 Webb, T., B. Rose, and A. H. Sehon, Can. J. Biochem. Physiol., 36, 1159 (1958).
    [Show full text]
  • Photosynthesis
    ENVIRONMENTAL PLANT PHYSIOLOGY SESSION 3 Photosynthesis An understanding of the biochemical processes of photosynthesis is needed to allow us to understand how plants respond to changing environmental conditions. This session looks at the details of the physiology and considers how plants can adapt these processes. If you studied the foundation degree with Myerscough previously you will recognise that much of these session notes are a very similar to those provided for the Plant Biology Module. The difference is not in the content but in the level of understanding required! Page Introduction to Photosynthesis 2 First catch your light! 3 The Light Dependent Reaction 7 The Light Independent Reaction 11 Photosynthesis and the Environment 12 Alternative Carbon Fixation Strategies 16 Further Reading 19 LEARNING OUTCOMES You need to be able to describe the biochemical basis of photosynthesis including: • Describing the role of chloroplasts and chlorophyll • Describing the steps of the light reaction and stating its products • Describing the Calvin cycle or light independent reaction and stating its products • Describing the role and position of the electron transport chain • Identify the effects of environmental factors on the rate of photosynthesis and explain how these relate to your field of study • Describe adaptations used by plants to continue photosynthesis in conditions of environmental stress such as hot arid conditions or shade conditions 1 Introduction to Photosynthesis The sun is the main source of energy to all living things. Light energy from the sun is converted to the chemical energy of organic molecules by green plants by a complicated pathway of reactions called photosynthesis.
    [Show full text]
  • Quantum Efficiency of Photosynthetic Energy Conversion (Photosynthesis/Photophosphorylation/Ferredoxin) RICHARD K
    Proc. Natl. Acad. Sd. USA Vol. 74, No. 8, pp. 3377-81, August 1977 Biophysics Quantum efficiency of photosynthetic energy conversion (photosynthesis/photophosphorylation/ferredoxin) RICHARD K. CHAIN AND DANIEL I. ARNON Department of Cell Physiology, University of California, Berkeley, Berkeley, California 94720 Contributed by Daniel I. Arnon, June 7,1977 ABSTRACT The quantum efficiency of photosynthetic with cyclic and noncyclic photophosphorylation and a "dark," energy conversion was investigated in isolated spinach chlo- enzymatic phase concerned with the assimilation of CO2 (8). roplasts by measurements of the quantum requirements of ATP has established that the formation by cyclic and noncyclic photophosphorylation cata- Fractionation of chloroplasts (9) light lyzed by ferredoxin. ATP formation had a requirement of about phase is localized in the membrane fraction (grana) that is 2 quanta per 1 ATP at 715 nm (corresponding to a requirement separable from the soluble stroma fraction which contains the of 1 quantum per electron) and a requirement of 4 quanta per enzymes of CO2 assimilation (10). Thus, in isolated and frac- ATP (corresponding to a requirement of 2 quanta per electron) tionated chloroplasts, investigations of photosynthetic quantum at 554 nm. When cyclic and noncyclic photophosphorylation efficiency can be focused solely on cyclic and noncyclic pho-. were operating concurrently at 554 nm, a total of about 12 account the conversion of quanta was required to generate the two NADPH and three ATP tophosphorylation, which jointly for needed for the assimilation of one CO2 to the level of glu- photon energy into chemical energy without the subsequent cose. or concurrent reactions of biosynthesis and respiration that cannot be avoided in whole cells.
    [Show full text]
  • Consequences of the Structure of the Cytochrome B6 F Complex for Its Charge Transfer Pathways ⁎ William A
    Biochimica et Biophysica Acta 1757 (2006) 339–345 http://www.elsevier.com/locate/bba Review Consequences of the structure of the cytochrome b6 f complex for its charge transfer pathways ⁎ William A. Cramer , Huamin Zhang Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA Received 17 January 2006; received in revised form 30 March 2006; accepted 24 April 2006 Available online 4 May 2006 Abstract At least two features of the crystal structures of the cytochrome b6 f complex from the thermophilic cyanobacterium, Mastigocladus laminosus and a green alga, Chlamydomonas reinhardtii, have implications for the pathways and mechanism of charge (electron/proton) transfer in the complex: (i) The narrow 11×12 Å portal between the p-side of the quinone exchange cavity and p-side plastoquinone/quinol binding niche, through which all Q/QH2 must pass, is smaller in the b6 f than in the bc1 complex because of its partial occlusion by the phytyl chain of the one bound chlorophyll a molecule in the b6 f complex. Thus, the pathway for trans-membrane passage of the lipophilic quinone is even more labyrinthine in the b6 f than in the bc1 complex. (ii) A unique covalently bound heme, heme cn, in close proximity to the n-side b heme, is present in the b6 f complex. The b6 f structure implies that a Q cycle mechanism must be modified to include heme cn as an intermediate between heme bn and plastoquinone bound at a different site than in the bc1 complex. In addition, it is likely that the heme bn–cn couple participates in photosytem + I-linked cyclic electron transport that requires ferredoxin and the ferredoxin: NADP reductase.
    [Show full text]
  • Chapter 19 Photophosphorylation
    Chapter 19 Part 3 Photophosphorylation Learning Goals: To Know 1. How energy of sunlight creates charge separation in the photosynthetic reaction complex and exciton transfer. 2. How electron transport is accompanied by the directional transport of protons across the membrane against their concentration gradient 3. Similarities and differences between plant-algal photosystems and bacterial photosystems. 4. How the electrochemical proton gradient drives synthesis of ATP by coupling the flow of protons via ATP synthase to conformational changes that favor formation of ATP in the active site 5. Roles of rhodopsins. Primary Production – Solar Energy Conversion Chloroplasts How do Photosynthetic Bacteria Fit in Here? Hill Reaction (driven by light) in Photophosphorylation 2 H2O + 2 A 2 AH2 + O2 “A” in Biological Systems = NADP+ so the Hill Reaction is: + + 2 H2O + 2 NADP 2 NADPH + 2H + O2 What Robert Hill in 1937 Actually Measured Was: The reduction of DCIP: going from blue to colorless. Electromagnetic Spectrum What is an Einstein? Light Energy Planck-Einstein Equation: E = h ν E = energy of a photon h = Planck’s Constant = 6.6 x 10-34 J.s v = vibration frequency ( of the wavelength of light; vibrational frequency increases with a decrease in wavelength ) In the text, E = hc/λ c/λ = v so red light, λ = 700 nm, c = 3x108m/s So that one red photon E = 2.83 x 10-19 J For an Einstein (a mole of photons) E = 168 kJ/einstein Chlorophyll a What is with the PINK ??? Phycobilins Carotenoids Photopigment Absorption Spectrum Chlorophyll Types Noon, Nov 18th: Surface Sun Light Spectra OE Pond Where is the Visible and Infra-red light ? Which one gets to the bottom? Noon, Nov 18th: Bottom The y-axis is in units of (einsteins/s)/m2 at each wavelength.
    [Show full text]
  • Effects of Low Concentrations of Ammonia and Methylamine
    Photophosphorylation by Chloroplasts: Effects of Low Concentrations of Ammonia and Methylamine Christoph Giersch Botanisches Institut der Universität Düsseldorf, Universitätsstr. 1, D-4000 Düsseldorf, Bundesrepublik Deutschland Z. Naturforsch. 37 c, 242-250 (1982); received December 23, 1981 Photophosphorylation, Uncoupling, Amines, Proton Motive Force, Chloroplasts, Chemiosmotic Theory Intact chloroplasts exposed to hypotonic assay conditions are capable of photophosphorylating exogenous ADP. The rate of phosphorylation by these unbroken plastids is increased by 10—50% upon the addition of low concentrations (< mM) of N H 3 or CH3NH 2. Stimulation of phosphory­ lation is abolished by washing chloroplasts with MgCl2. Evidence is presented that washing re­ moves a factor responsible for amine-induced increase of A TP production and that this factor is associated with the thylakoid membrane. Addition of CH3NH 2 increased the proton permeability of the thylakoid membrane of unbroken and washed chloroplasts during the light/dark transition. Hence, differences of the membrane permeability for protons between the two preparations seem not to be responsible for an increase of ATP production upon the addition of amines. Stimulation of photophosphorylation by methylamine is observed even at light itensities which do not saturate the proton motive force, which in turn is reduced upon the addition of the uncoupler. Apparently, phosphorylation can be stimulated, although the limiting driving force is diminished. It is con­ cluded that phosphorylation by unbroken chloroplasts under low light illumination is limited kinetically, not energetically. Consequences of these findings for observation made with intact chloroplasts are discussed. Introduction creased pmf in the presence of low amine * concen­ trations although the rate of steady-state light-de­ The chemiosmotic concept holds the trans­ pendent ATP production is increased [4].
    [Show full text]
  • BOOK REVIEWS Genes, Organisms, Populations: Controversies Over the Units of Selection Edited by Robert N
    BOOK REVIEWS Genes, organisms, populations: Controversies over the units of selection edited by Robert N. Brandon and Richard M. Burian. The MIT Press, Cambridge, Massachusetts, USA, 1984, -pp. xiv + 329, $ 34.44. He is a collection of papers on natural selection published over the'past 25 years. The unit (or units) of selection is the subject of discussion. Charles Darwin felt that the individual was the target of selection, not races, groups or populations. Alfred Wallace, on the other hand, thought that selection acted on groups in addition to the individual. Against this historical background of the two originators of the idea of natural selection, the editors have put together current views of selection, the levels as well as the units on which selection a&. The papers are grouped under three heads: Historical readings; Levels and units of selection; Models of selection. Each part has an introduction, contributed by the editors, who as students of philosophy appear to have found some sudden and unexplained interest in problems of evolution. Several of the papers included in the volume were written long before the question of natural selection hotted up some five years ago and so are of limited interest. Nevertheless, they are of considerable influence in determining the level at which selection is believed to operate. The main thrust of selection at levels higher than the individual level is offered by Altruism, which Darwin was clearly unaware of and which has only recently come to the fore. Seemingly contradictory, the different levels harmonize at a certain order; it seems to be the endeavour of the authors to find this conformation.
    [Show full text]
  • Do We Have a Thermotrophic Feature? James Weifu Lee
    www.nature.com/scientificreports OPEN Mitochondrial energetics with transmembrane electrostatically localized protons: do we have a thermotrophic feature? James Weifu Lee Transmembrane electrostatically localized protons (TELP) theory has been recently recognized as an important addition over the classic Mitchell’s chemiosmosis; thus, the proton motive force (pmf) is largely contributed from TELP near the membrane. As an extension to this theory, a novel phenomenon of mitochondrial thermotrophic function is now characterized by biophysical analyses of pmf in relation to the TELP concentrations at the liquid-membrane interface. This leads to the conclusion that the oxidative phosphorylation also utilizes environmental heat energy associated with the thermal kinetic energy (kBT) of TELP in mitochondria. The local pmf is now calculated to be in a range from 300 to 340 mV while the classic pmf (which underestimates the total pmf) is in a range from 60 to 210 mV in relation to a range of membrane potentials from 50 to 200 mV. Depending on TELP concentrations in mitochondria, this thermotrophic function raises pmf signifcantly by a factor of 2.6 to sixfold over the classic pmf. Therefore, mitochondria are capable of efectively utilizing the environmental heat energy with TELP for the synthesis of ATP, i.e., it can lock heat energy into the chemical form of energy for cellular functions. In the past, there was a common belief that the living organisms on Earth could only utilize light energy and/ or chemical energy, but not the environmental heat energy. Consequently, the life on Earth has been classifed as two types based on their sources of energy: phototrophs and chemotrophs.
    [Show full text]
  • BBA - Bioenergetics 1860 (2019) 433–438
    BBA - Bioenergetics 1860 (2019) 433–438 Contents lists available at ScienceDirect BBA - Bioenergetics journal homepage: www.elsevier.com/locate/bbabio Review The mechanism of cyclic electron flow T ⁎ W.J. Nawrockia,b, , B. Bailleula, D. Picotc, P. Cardolb, F. Rappaporta,1, F.-A. Wollmana, P. Joliota a Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 rue P. et M. Curie, 75005 Paris, France b Laboratoire de Génétique et Physiologie des Microalgues, Institut de Botanique, Université de Liège, 4, Chemin de la Vallée, B-4000 Liège, Belgium c Institut de Biologie Physico-Chimique, UMR 7099 CNRS-UPMC, 13 rue P. et M. Curie, 75005 Paris, France ARTICLE INFO ABSTRACT Keywords: Apart from the canonical light-driven linear electron flow (LEF) from water to CO2, numerous regulatory and Photosynthesis alternative electron transfer pathways exist in chloroplasts. One of them is the cyclic electron flow around Biophysics Photosystem I (CEF), contributing to photoprotection of both Photosystem I and II (PSI, PSII) and supplying extra Plastoquinone ATP to fix atmospheric carbon. Nonetheless, CEF remains an enigma in the field of functional photosynthesis as Cytochrome b f 6 we lack understanding of its pathway. Here, we address the discrepancies between functional and genetic/ Photosystem I biochemical data in the literature and formulate novel hypotheses about the pathway and regulation of CEF Cyclic electron flow based on recent structural and kinetic information. 1. Linear and cyclic electron flow kinetic and methodological standpoint in the light of our report that PGRL1 is not directly transferring electrons from Fd to PQ during CEF Photosynthesis consists of a photoinduced linear electron flow [1].
    [Show full text]
  • Chemiosmosis - the Mechanism of ATP Synthesis in Chloroplasts
    Chemiosmosis - The Mechanism of ATP Synthesis in Chloroplasts The thylakoid membrane is composed of a phospholipid bilayer (color phospholipids "B" light blue) and photosystem I and photosystem II. Although they both work simultaneously, it is best to look at them one at a time, starting with photosystem II. The first and most important event in either system is the capturing of light energy (color "E" orange) by the pigments associated with each photosystem. Color the pigments of Photosystem II (P2) dark green and the pigments of Photosystem I (P1) light green. Pigment 680 (color dark green) is associated with Photosystem II, and Pigment 700 (color light green) is associated with Photosystem I. When a photon of light strikes the reaction center of Photosystem II, it excites an electron. Two water molecules bind to an enzyme that splits water into hydrogen ions (protons) and releases an oxygen atom. Color the protons (H+) yellow and the oxygen atoms (O2) red. This process is called PHOTOLYSIS and is illustrated by the arrows labeled "L", which you should color pink. Two electrons are released in this process, and these electrons can be traced through photosystem II and photosystem I. Color the electrons (e) grey. Two oxygen atoms will join together to create an oxygen molecule which is released from the plant as a byproduct of the entire reaction. The primary electron acceptor for the light-energized electrons leaving photosystem II is plastoquinone (color PQ purple). The reduced plastoquinone passes the excited electrons to a proton pump embedded in the membrane called the b6-f complex (color dark blue).
    [Show full text]