DOCSLIB.ORG

Tryptophan Repressor of Escherichia Coli Shows Unusual

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Tryptophan Repressor of Escherichia Coli Shows Unusual Proc. Nat!. Acad. Sci. USA Vol. 85, pp. 6731-6732, September 1988 Biophysics Tryptophan repressor of Escherichia coli shows unusual thermal stability (protein denaturation/scanning calorimetry) SONG-JA BAE*, WEI-YUAN CHOUt, KATHLEEN MATTHEWSt, AND JULIAN M. STURTEVANT* *Departments of Chemistry and of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511; and tDepartment of Biochemistry, Rice University, Houston, TX 77251 Contributed by Julian M. Sturtevant, June 13, 1988 ABSTRACT Differential scanning calorimetry demon- strates that the tryptophan repressor of Escherichia coli is unusually resistant to thermal denaturation. The dimeric protein undergoes reversible dissociative unfolding at pH 7.5 I-w centered at about 900C. The thermal stability may be due in part to the unusual structure of the protein, which is composed U. of two identical intertwined polypeptide chains. LU u) The tryptophan (trp) repressor from Escherichia coli is Cf) involved in regulating the expression of biosynthetic en- CU) zymes for tryptophan in response to the level of this amino x acid in the cell. Tryptophan binds to the repressor and increases its affinity for the operator target site within the trp promoter, thereby preventing transcription initiation. The trp repressor protein is a dimer of molecular weight 24,700 (1) TEMPERATURE,,C with two binding sites for tryptophan and a single operator DNA binding site. The three-dimensional structure of this FIG. 1. Tracings ofDSC scans oftrp repressor after deduction of protein has been determined (2). The monomer structure the instrument baseline. Protein concentration was 255 ,uM in 0.05 M consists of six helical regions, which are intertwined with the phosphate buffer, pH 7.0/0.1 M NaCl. The scan rate was 1 Kemin - 1. corresponding helices ofthe companion monomerto form the The first scan (curve A) was interrupted at 100TC, the protein solution dimeric structure. The significant intersubunit was cooled in situ over a period of about 30 min and then was contacts seen rescanned (curve B). The dashed lines are the pre- and post- in the crystallographic analysis suggest that a stable dimeric transition baselines. The tracings illustrate realistically the very low structure might be anticipated for this protein. We report here noise level of the original recordings. the results of differential scanning calorimetric (DSC) exper- iments that show trp repressor to be remarkably thermally weight; no contaminants were detected when the gel was stable and will report elsewhere more detailed data of the overloaded. effects on the thermal denaturation of variations in pH, the Before introduction into the calorimeter, the protein was addition ofligands, and other experimental conditions as well dialyzed against 10 mM potassium phosphate/100 mM KCl, as the replacement of single amino acid residues. pH 7.5. The dialysate served as the reference solution in the calorimeter. Protein concentrations were estimated by taking MATERIALS AND METHODS the absorption of a 1 mg-ml-1 solution to be 1.20. The tryptophan repressor was isolated in the following The DSC experiments were run at a scan rate of 1 K-min' manner. Bacterial cells containing a multicopy plasmid in a DASM4 scanning microcalorimeter (5) purchased from (pJPR2) that overproduces the trp repressor were obtained Mashpriborintorg, Moscow. from C. Yanofsky (Stanford University). Procedures for cell growth were those described by Paluh and Yanofsky (3). The RESULTS AND DISCUSSION protein was purified by using the procedure ofJoachimiak et al. (4) with the changes delineated below. The cell suspension A tracing of a typical DSC curve is shown in Fig. 1. As was sonicated 30 ml at a time for a total duration of3 min (the indicated in the tracing, no noise was visible in the original cycle was sonication for 30 s followed by cooling for 30 s). recording. The initial scan (curve A) was interrupted at The ammonium sulfate pellet was suspended in 0.01 M 100TC, the material was cooled over a period of 30 min in the potassium phosphate, pH 7.4/0.1 mM EDTA/0.2 M KCl, and calorimeter, and then it was rescanned (curve B). It is evident the suspension was dialyzed against this buffer. After dialy- that the denaturation was essentially fully reversed during the sis, the sample was applied directly to a phosphocellulose cooling, showing this to be a most unusually thermally stable column equilibrated in sample buffer, and the column was protein. It seems likely that this stability is at least in part due developed with the same buffer. The trp repressor was eluted to the unusual structure of the protein, with intertwined by sample buffer containing 0.5 M KCl. The fractions polypeptide chains. containing the repressor were pooled and concentrated to :8 The curves in Fig. 1 are asymmetric, being sharper on the mg/ml. Polyacrylamide gel electrophoresis of the purified high-temperature side than on the low-temperature side. A protein yielded a single component ofthe expected molecular possible cause of this type of asymmetry is a decrease in the extent of oligomerization during the transition (6). It was The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" Abbreviation: DSC, differential scanning calorimeter (calorimetric, in accordance with 18 U.S.C. §1734 solely to indicate this fact. calorimetry). 6731 Downloaded by guest on September 29, 2021 6732 Biophysics: Bae et al. Proc. Natl. Acad. Sci. USA 85 (1988) Table 1. The thermal unfolding of tryptophan repressor at pH 7.5 AHvH, kcal mol Protein, AHc,,, Curve Ace, SD, AuM tmi, C tA2, 0C kcal-mol-' fitting Eq. 1 cal-K-g-1 % cexa 70.4 90.8 90.80 74.0 126 128 -0.034 1.8 102.0 91.6 91.55 71.0 135 131 -0.037 3.7 136.0 92.6 90.25 100.8 103 102 0.035 3.5 142.8 92.2 88.47 97.3 91 88 0.136 2.8 204 92.7 90.26 87.3 108 108 0.081 1.3 255 93.5 90.14 106.0 100 100 0.086 2.2 340 93.5 90.39 100.8 98 98 0.087 4.1 676 94.0 90.41 95.3 95 95 0.118 2.5 Mean ± SEM 90.30 ± 0.35 91.6 ± 5.3 107 ± 6 106 ± 6 0.059 ± 0.027 2.6 ± 0.5 found that the data could be fit with reasonably small standard concentrations, values for AHVH (column 6) calculated by deviations to the model A2 a± 2B, using the calculational means of the equation procedure outlined earlier (7). Fig. 2 illustrates the closeness of fit obtained. In Fig. 2 the solid line represents the observed data, AHVH = ARTi12 &/29 [l] the filled circles represent the calculated values, and the dashed A/Rcal curve represents the calculated baseline. The initial and final where the factor A has the value 6 for the dissociative baselines (not shown) were evaluated by linear least-squares denaturation ofa dimeric species, agree reasonably well with treatment ofthe data obtained at temperatures below 67TC and AH,.,; In this expression Ti,2 is the absolute temperature at above 1050C. half completion of the denaturation, c",1/2 is the apparent excess specific heat at this temperature, and Ah~a is the Data for eight experiments are summarized in Table 1. For specific denaturational enthalpy. unknown reasons, the calorimetric enthalpies were low and If the assumed model is' appropriate for this system, an the van't Hoffenthalpies were high for the experiments at the additional value for AHVH should be given by -RS, where S two lowest protein concentrations, and negative values were is the slope of a van't Hoff plot of ln[P]. vs 1/Tm or 1/Ti/2. observed for Ace, the excess specific heat. The validity ofthe [P]0 is the total protein concentration, and Tm is the absolute assumed model is supported by the close agreement between temperature at which the excess specific heat is maximal. It the values for the van't Hoffenthalpy, AHvH, obtained in the is evident that the values of ti,2 = Ti,2 - 273.15 remain curve fitting (column 6 in Table 1) with those for the constant within experimental uncertainty. A van't Hoff plot calorimetric enthalpy, AHIaI (column 5). Further support for using Tm leads to AHVH = 169 kcalmol- 1, with a coefficient the model is given by the fact that, at the six highest protein of determination r2 = 0.90. This enthalpy value is nearly twice as large as expected. We can offer no explanation at 0.40 present for this discrepancy or for the apparent insensitivity of ti,/ to protein concentration. It is evident in Fig. 2 that the post-transition baseline has a negative slope, as was observed also in nearly all the other experiments. It is unusual for a protein to have its apparent specific heat decrease with increasing temperature. In view 0.3) F of the fact that the behavior of'the calorimeter is somewhat 8cm less reliable at very high temperatures than in the more usual ,..d temperature range, further work is required to establish the 9-2 validity of the -a observation of an abnormal temperature co -W dependence of the specific heat. Li 0.20 F We have mentioned several abnormalities encountered in C-) the present work which we CL) hope will be resolved by further C=L cn research. Despite these complications, we have firmly es- U) CL. tablished that the stability ofthe trp repressor against thermal Li D.< LL.j unfolding is most unusual and that the unfolded protein also resists irreversible degradation of its separated polypeptide D.to01 chains to an unusual degree.
Load more

Recommended publications
  • 16.1 | Regulation of Gene Expression
    436 Chapter 16 | Gene Expression 16.1 | Regulation of Gene Expression By the end of this section, you will be able to do the following: • Discuss why every cell does not express all of its genes all of the time • Describe how prokaryotic gene regulation occurs at the transcriptional level • Discuss how eukaryotic gene regulation occurs at the epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels For a cell to function properly, necessary proteins must be synthesized at the proper time and place. All cells control or regulate the synthesis of proteins from information encoded in their DNA. The process of turning on a gene to produce RNA and protein is called gene expression. Whether in a simple unicellular organism or a complex multi-cellular organism, each cell controls when and how its genes are expressed. For this to occur, there must be internal chemical mechanisms that control when a gene is expressed to make RNA and protein, how much of the protein is made, and when it is time to stop making that protein because it is no longer needed. The regulation of gene expression conserves energy and space. It would require a significant amount of energy for an organism to express every gene at all times, so it is more energy efficient to turn on the genes only when they are required. In addition, only expressing a subset of genes in each cell saves space because DNA must be unwound from its tightly coiled structure to transcribe and translate the DNA. Cells would have to be enormous if every protein were expressed in every cell all the time.
    [Show full text]
  • Formation of Heterodimers Between Wild Type and Mutant Trp Aporepressor Polypeptides of Eschem'chia Coli Thomas J
    PROTEINS: Structure, Function, and Genetics 4:173-181 (1988) Formation of Heterodimers Between Wild Type and Mutant trp Aporepressor Polypeptides of Eschem'chia coli Thomas J. Graddis,' Lisa S. Klig,' Charles Yanofsky,' and Dale L. Oxender' 'Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109 and 'Department of Biological Sciences, Stanford University, Stanford, California 94305 ABSTRACT Availability of the three-dimen- tophan.1-6 The trp aporepressor is activated by the sional structure of the trp repressor of Escherichia binding of two molecules of its corepressor. Once ac- coli and a large group of repressor mutants has per- tivated, trp repressor binds to the operators of the trp, mitted the identification and analysis of mutants aroH, and trpR operons, regulating transcription ini- with substitutions of the amino acid residues that tiati~n.~,'The aroH and trp operons encode biosyn- form the tryptophan binding pocket. Mutant apore- thetic enzymes, whereas the trpR operon encodes the pressors selected for study were overproduced using trp aporepressor. The trpR gene has been cloned and a multicopy expression plasmid. Equilibrium di- its nucleotide sequence determined.3 The aporepres- alysis with ''C-tryptophan and purified mutant and sor and repressor have been purified and the crystal wild type aporepressors was employed to determine structures of both have been solved at high resolu- tryptophan binding constants. The results obtained ti~n.~-"The trp aporepressor is a dimer of identical indicate that replacement of threonine 44 by methi- 107 residue polypeptides." The existence of the three- onine (TM44) or arginine 84 by histidine (RH84) low- dimensional structures, and the availability of many ers the affinity for tryptophan approximately two- repressor mutants,2i12has facilitated this analysis of and four-fold, respectively.
    [Show full text]
  • Application of Models for Biomolecular Structure and Interactions to Understand and Influence Biological Function
    Application of Models for Biomolecular Structure and Interactions to Understand and Influence Biological Function Zur Erlangung des akademischen Grades eines DOKTORS DER NATURWISSENSCHAFTEN (Dr. rer. nat.) Fakultät für Chemie und Biowissenschaften Karlsruher Institut für Technologie (KIT) - Universitätsbereich genehmigte DISSERTATION von Irene Meliciani aus Rom (Italien) Dekan: Prof. Dr. Martin Bastmeyer Referent: Prof. Dr. Stefan Bräse Korreferent: Apl. Prof. Dr. Wolfgang Wenzel Tag der mündlichen Prüfung: 19.10.2011 a mamma e papà Application of Models for Biomolecular Structure and Interactions to Understand and Influence Biological Function Irene Meliciani Karlsruher Institut für Technologie Institut für Nanotechnologie Intitut für Organische Chemie Zusammenfassung Die Forschung in den Lebenswissenschaften hat in den letzten Jahrzehnten zu einem enormen Wissensgewinns bezüglich der Abläufe zellulärer Prozesse und ihrer Steuerung geführt. Die Steuerung biologischer Prozesse wird vielfach über Kontaktwechselwirkungen der daran beteiligten Biomoleküle bewältigt. Mit dieser Arbeit möchte ich zu einem besseren Verständnis biomolekularer Interaktionen beitragen. Ein Teil dieser Arbeit beschäftigt sich mit der Untersuchung von Proteininteraktionen, wobei als Methoden für die Modellierung von Protein-Protein-Wechselwirkungen (POEM) und für die Protein-Liganden-Wechselwirkung (FLEXSCREEN) eingesetzt wurden. Es wurden die Interaktionen der Chemokinrezeptoren CCR3 und CXCR1 mit für den Entzündungsverlauf wichtigen Steuerungsmolekülen (Chemokinen)
    [Show full text]
  • Teaching Gene Regulation in the High School Classroom, AP Biology, Stefanie H
    Wofford College Digital Commons @ Wofford Arthur Vining Davis High Impact Fellows Projects High Impact Curriculum Fellows 4-30-2014 Teaching Gene Regulation in the High School Classroom, AP Biology, Stefanie H. Baker Wofford College, [email protected] Marie Fox Broome High School Leigh Smith Wofford College Follow this and additional works at: http://digitalcommons.wofford.edu/avdproject Part of the Biology Commons, and the Genetics Commons Recommended Citation Baker, Stefanie H.; Fox, Marie; and Smith, Leigh, "Teaching Gene Regulation in the High School Classroom, AP Biology," (2014). Arthur Vining Davis High Impact Fellows Projects. Paper 22. http://digitalcommons.wofford.edu/avdproject/22 This Article is brought to you for free and open access by the High Impact Curriculum Fellows at Digital Commons @ Wofford. It has been accepted for inclusion in Arthur Vining Davis High Impact Fellows Projects by an authorized administrator of Digital Commons @ Wofford. For more information, please contact [email protected]. High Impact Fellows Project Overview Project Title, Course Name, Grade Level Teaching Gene Regulation in the High School Classroom, AP Biology, Grades 9-12 Team Members Student: Leigh Smith High School Teacher: Marie Fox School: Broome High School Wofford Faculty: Dr. Stefanie Baker Department: Biology Brief Description of Project This project sought to enhance high school students’ understanding of gene regulation as taught in an Advanced Placement Biology course. We accomplished this by designing and implementing a lab module that included a pre-lab assessment, a hands-on classroom experiment, and a post-lab assessment in the form of a lab poster. Students developed lab skills while simultaneously learning about course content.
    [Show full text]
  • Mutant Tryptophan Aporepressors with Altered Specificities Of
    Copyright 0 1991 by the Genetics Society of America Mutant Tryptophan Aporepressors With Altered Specificitiesof Corepressor Recognition Dennis N. Arvidson,' Michael Shapiro' and Philip Youderian' Department of Biological Sciences, University of Southern Calqornia, Los Angeles, Calqornia 90089 Manuscript received November 20, 1990 Accepted for publication January 19, 199 1 ABSTRACT The Escherichia coli trpR gene encodes tryptophan aporepressor, which binds the corepressor ligand, L-tryptophan, to form an active repressor complex. The side chain of residue valine 58 of Trp aporepressor sits at the bottom of the corepressor @-tryptophan) binding pocket. Mutant trpR genes encoding changes of Vals8 to the other 19 naturally occurring amino acids were made. Each of the mutant proteins requires a higher intracellular concentration of tryptophan for activation of DNA binding than wild-type aporepressor. Whereas wild-type aporepressor is activated better by 5- methyltryptophan (5-MT) than by tryptophan, IlesHand other mutant aporepressors prefer tryptophan to 5-MT as corepressor, and Ala5' and GIY'~prefer 5-MT much more strongly than wild-type aporepressor in vivo. These mutant aporepressors are the first examples of DNA-binding proteins with altered specificities ofcofactor recognition. ANY regulatory proteins areallosteric, and bind intermonomer interactions stabilize its extraordinary M small metabolic intermediates that modify their hydrophobic core. The aporepressor dimer denatures activities, allowing the intracellular pattern of gene at a very high temperature (>go") (BAEet al. 1988). expression to respond to physiologicalchange. For Comparisons of the crystal structures of repressor example, the Escherichia coli tryptophan aporepressor (SCHEVITZet al. 1985; LAWSONet al. 1988;OTWI- (TrpR) protein binds DNA poorly. However, when NOWSKI et al.
    [Show full text]
  • Development of Novel Transgenic Zebrafish
    DEVELOPMENT OF NOVEL TRANSGENIC ZEBRAFISH MODELS AND THEIR APPLICATION TO STUDIES ON ENVIRONMENTAL OESTROGENS Submitted by Jon Marc Green to the University of Exeter as a thesis for the degree of Doctor of Philosophy in Biological Sciences, September 2016 This thesis is available for Library use on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. I certify that all material in this thesis which is not my own work has been identified and that no material has previously been submitted and approved for the award of a degree by this or any other University. (Signature) ……………………………………………(Jon Marc Green) 1 Abstract Oestrogenic chemicals have become increasingly associated with health effects in wildlife populations and humans. Transgenic animal models have been developed to understand the mechanisms by which these oestrogenic chemicals alter hormonal signalling pathways and how these alterations can lead to chronic health effects. The use of highly informative transgenic animal models will also result in better use and potential reduction of intact animals used in animal testing in line with the principles of the 3Rs. In this thesis work, two novel oestrogen responsive transgenic zebrafish models have been generated to investigate the effects of oestrogenic chemicals, identify their tissue targets and better understand the temporal dynamics of these responses. Both models express the pigment-free ‘Casper’ (a mutant line lacking skin pigment) phenotype, which facilitate identification of responding target tissues in the whole fish in all fish life stages (embryos to adults). The oestrogen response element green fluorescent (ERE-GFP)-Casper model was generated by crossing an established ERE-GFP line with the skin pigment free Casper line.
    [Show full text]
  • Binds Multiple Sites Within the Aroh and Trp Operators
    Downloaded from genesdev.cshlp.org on September 30, 2021 - Published by Cold Spring Harbor Laboratory Press Escherichia cod tryptophan repressor binds multiple sites within the aroH and trp operators Andrew A. Kumamoto, ~ William G. Miller, 2 and Robert P. GunsalusL2 1Molecular Biology Institute and the 2Department of Microbiology, University of Califomia, Los Angeles, Califomia 90024 USA DNase I footprinting and methylation protection studies have been used to analyze the binding of Escherichia coli Trp repressor to the trpR, aroH, and trp operators. The methylation protection assay shows that Trp repressor binds in two successive major grooves of the trpR operator, three successive major grooves of the aroH operator, and four successive major grooves of the trp operator. The simplest model that explains the difference in Trp repressor interaction at the three operators is that the aroH and trp operators are composed of multiple, helically stacked binding sites. When viewed in three dimensions, each site is positioned on a different face of the DNA, and together process up the surface of the DNA helix. Analysis of a deletion derivative of the trp operator supports this model. [Key Words" Trp repressor; aroH operator; trp operator; repressor binding] Received February 23, 1987; revised version accepted June 6, 1987. The Trp repressor of Escherichia coli coordinately regu- and by the isolation of constitutive mutations within lates the expression of the trp, aroH, and trpR operons in the trp operator {Bennett and Yanofsky 1978). These op- response to the intracellular levels of L-tryptophan erator constitutive mutations map at positions -16, (Cohen and Jacob 1959; Brown 1968; Rose et al.
    [Show full text]
  • Pathogen Xylella Fastidiosa
    articles The genome sequence of the plant pathogen Xylella fastidiosa The Xylella fastidiosa Consortium of the Organization for Nucleotide Sequencing and Analysis*,Sa˜o Paulo, Brazil * A full list of authors appears at the end of this paper ............................................................................................................................................................................................................................................................................ Xylella fastidiosa is a fastidious, xylem-limited bacterium that causes a range of economically important plant diseases. Here we report the complete genome sequence of X. fastidiosa clone 9a5c, which causes citrus variegated chlorosis—a serious disease of orange trees. The genome comprises a 52.7% GC-rich 2,679,305-base-pair (bp) circular chromosome and two plasmids of 51,158 bp and 1,285 bp. We can assign putative functions to 47% of the 2,904 predicted coding regions. Efficient metabolic functions are predicted, with sugars as the principal energy and carbon source, supporting existence in the nutrient-poor xylem sap. The mechanisms associated with pathogenicity and virulence involve toxins, antibiotics and ion sequestration systems, as well as bacterium–bacterium and bacterium–host interactions mediated by a range of proteins. Orthologues of some of these proteins have only been identified in animal and human pathogens; their presence in X. fastidiosa indicates that the molecular basis for bacterial pathogenicity is both conserved and independent of host. At least 83 genes are bacteriophage-derived and include virulence-associated genes from other bacteria, providing direct evidence of phage-mediated horizontal gene transfer. Citrus variegated chlorosis (CVC), which was first recorded in Brazil meningitidis10 (53.7%). This may reflect the lack of previous in 1987, affects all commercial sweet orange varieties1. Symptoms complete genome sequences from phytopathogenic bacteria.
    [Show full text]
  • The Tryptophan Biosynthetic Pathway Trp Biosynthesis Is a Biologically Expensive, Complicated Process
    E. Coli Trp repressor The tryptophan repressor proteins The trp repressor proteins regulate transcription of several diferent operons located at separate sites on the E. coli chromosome. In addition to the trp operon, this repressor represses transcription of aroH, a single-gene operon that encodes an enzyme required for the synthesis of all aromatic amino acids, and trpR, another single-gene operon encoding the trp repressor itself. Such coordinately regulated operons constitute a regulon. Although all three operons in this regulon are repressed by the trp repressor, the extent of repression varies from about twofold for the aroH operon to seventyfold for the trp operon. This variation results from diferences in the afnity of trp repressor for the specific operator in each of these operons, diferences in the position of the operators relative to the −10 and −35 sequences of each promoter, and diferences in the strengths of the three promoters. Thus the specific nucleotide sequences of the promoters and operators in a regulon allow the same repressor to diferentially regulate transcription of the component operons. The tryptophan biosynthetic pathway Trp biosynthesis is a biologically expensive, complicated process. In fact, the products of four other pathways are essential contributors of carbon or nitrogen during tryptophan formation. Thus, the principal pathway precursor, chorismate, is also the precursor of the other aromatic amino acids, phenylalanine and tyrosine, as well as serving as the precursor of p- aminobenzoic acid and several other metabolites. In addition, glutamine, phosphoribosylpyrophosphate, and L-serine contribute nitrogen and/or carbon during tryptophan formation. FIGURE 1. The genes, enzymes, and reactions of the tryptophan biosynthetic pathway.
    [Show full text]
  • Welcome to Part 3 of Bio 219
    Welcome to Part 3 of Bio 219 Lecturer – David Ray Contact info: Office hours – 1:00-2:00 pm MTW Office location – LSB 5102 Office phone – 293-5102 ext 31454 E-mail – [email protected] Lectures and other resources are available online at http://www.as.wvu.edu/~dray. Go to ‘Courses’ link Chapter 12: The Cell Nucleus and Control of Gene Expression The Cell Nucleus… • Every somatic cell contains the same genetic information regardless of whether it is expressed the same way. • Just as in a building under construction, all workers have access to the complete set of blueprints. • However, the workers constructing the floors only use the information related to their word and the workers installing the wiring only use the information related to their project. • Brain cells only express genes related to brain activity and liver cells only express the genes related to their activity. The Cell Nucleus… • The nucleus of most cells is typically amorphous and consists of: – The chromosomes (in the form of chromatin) – Nucleoli – Nucleoplasm – The nuclear matrix • All surrounded by the nuclear envelope The Cell Nucleus… • The nuclear envelope is complex; consists of several distinct components: 2 cellular membranes arranged parallel to one another & separated by 10 - 50 nm – Separates genetic material in nucleus from cytoplasm - important distinction between prokaryotes & eukaryotes; its appearance is an evolutionary landmark • 1. Serves as barrier; keeps ions, solutes, macromolecules from passing between nucleus & cytoplasm The Cell Nucleus… • The nuclear envelope… – B. Fused at sites forming circular pores that contain complex assemblies of proteins • 1. Average mammalian cell: contains ~3000 nuclear pores • 2.
    [Show full text]
  • Dna Binding Domains in Eukaryotic Transcription Factors
    Dna Binding Domains In Eukaryotic Transcription Factors Tre convulsing her tramplings harmfully, inappeasable and animalic. Which Manny phonate so plumb that Ted rankling her rails? Glairiest and unhinged Sandy never womanise peradventure when Allie overstrides his scourers. Dna with the dna binding components in eukaryotic transcription in factors binding dna binding strength of related. If they bind both the building blocks cookies must traverse the vicinity of factors binding dna in transcription factors are? What do not give rise to eukaryotic proteins bind to improve computational approaches and domain that favors aggregation during folding is able to improve customer experience. These domains are comparable domain. What two domains are eukaryotic rna polymerase are? Article you have these factors binding dna sequences using clustering by calculating differences for eukaryotic transcription factor binds. Pictorial representation overlaid, eukaryotic transcription are turned off multiple isoforms have discovered that at concentration. We vary from each of their regulation of transcription through this eukaryotic transcription. The label for statistically overrepresented motifs are also cause a transcription. Two proteins are to accept cookies from four separate lines or due to do? Irradiation of sequence similarity between length of three transcription factors to promote and expressed, a first combining chemical process. Myc is basic residues whose side, factors and dna, genetic information possible by chance if you have been associated with structural unit. Gene regulation or decreased gene editing. An important regulatory domain. This dna binding factors. Xt pondr prediction accuracy of transcriptional regulators of binding factors: a plausible model due to detect. Double fortification of eukaryotic transcription machinery and eukaryotic transcription in dna binding domains.
    [Show full text]
  • DNA Microarray Analysis of Gene Expression in Response to Physiological and Genetic Changes That Affect Tryptophan Metabolism in Escherichia Coli
    DNA microarray analysis of gene expression in response to physiological and genetic changes that affect tryptophan metabolism in Escherichia coli Arkady B. Khodursky*, Brian J. Peter†, Nicholas R. Cozzarelli†, David Botstein‡, Patrick O. Brown*§, and Charles Yanofsky¶ʈ Departments of *Biochemistry and ‡Genetics, §Howard Hughes Medical Institute, Stanford University School of Medicine, and ¶Department of Biological Sciences, Stanford University, Stanford, CA 94305; and †Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720 Contributed by Charles Yanofsky, August 29, 2000 We investigated the global changes in mRNA abundance in Esche- uation as well as by repression (1, 2, 9, 11). The aroH operon richia coli elicited by various perturbations of tryptophan metabolism. specifies one of three nearly identical enzymes (the other two are To do so we printed DNA microarrays containing 95% of all annotated specified by aroF and aroG) that catalyze the first reaction in the E. coli ORFs. We determined the expression profile that is predomi- common pathway of aromatic amino acid biosynthesis (12). The mtr nantly dictated by the activity of the tryptophan repressor. Only three operon encodes a tryptophan-specific permease (13, 14), the trpR operons, trp, mtr, and aroH, exhibited appreciable expression operon encodes the trp aporepressor (15, 16), and the aroL operon changes consistent with this profile. The quantitative changes we encodes one of two enzymes that catalyze the same reaction in the observed in mRNA levels for the five genes of the trp operon were common aromatic pathway (17, 18). The mtr and aroL operons are consistent within a factor of 2, with expectations based on estab- also transcriptionally regulated by TyrR, the general aromatic lished Trp protein levels.
    [Show full text]