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Sharma S, Gollnick P. Modulating TRAP-mediated transcription termination by AT during transcription of the leader region of the Bacillus subtilis trp operon. Nucleic Acids Res 2014; 42:5543-55. [PMID: 24682818 PMCID: PMC4027176 DOI: 10.1093/nar/gku211] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
An 11-subunit protein called trpRNA binding Attenuation Protein (TRAP) controls attenuation of the tryptophan biosynthetic (trpEDCFBA) operon in Bacillus subtilis. Tryptophan-activated TRAP binds to 11 (G/U)AG repeats in the 5′ leader region of trp mRNAs, and downregulates expression of the operon by promoting transcription termination prior to the structural genes. Anti-TRAP (AT) is an antagonist that binds to tryptophan-activated TRAP and prevents TRAP from binding to RNA, thereby upregulating expression of the trp genes. AT forms trimers, and multiple trimers bind to a TRAP 11mer. It is not known how many trimers must bind to TRAP in order to interfere with RNA binding. Studies of isolated TRAP and AT showed that AT can prevent TRAP from binding to the trp leader RNA but cannot dissociate a pre-formed TRAP-RNA complex. Here, we show that AT can prevent TRAP-mediated termination of transcription by inducing dissociation of TRAP from the nascent RNA when it has bound to fewer than all 11 (G/U)AG repeats. The 5′-most region of the TRAP binding site in the nascent transcript is most susceptible to dissociation from TRAP. We also show that one AT trimer bound to TRAP 11mer reduces the affinity of TRAP for RNA and eliminates TRAP-mediated transcription termination in vitro.
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Affiliation(s)
- Shraddha Sharma
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Paul Gollnick
- Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
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Ihms EC, Zhou M, Zhang Y, Kleckner IR, McElroy CA, Wysocki VH, Gollnick P, Foster MP. Gene regulation by substoichiometric heterocomplex formation of undecameric TRAP and trimeric anti-TRAP. Proc Natl Acad Sci U S A 2014; 111:3442-7. [PMID: 24550461 PMCID: PMC3948263 DOI: 10.1073/pnas.1315281111] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The control of tryptophan production in Bacillus is a paradigmatic example of gene regulation involving the interplay of multiple protein and nucleic acid components. Central to this combinatorial mechanism are the homo-oligomeric proteins TRAP (trp RNA-binding attenuation protein) and anti-TRAP (AT). TRAP forms undecameric rings, and AT assembles into triskelion-shaped trimers. Upon activation by tryptophan, the outer circumference of the TRAP ring binds specifically to a series of tandem sequences present in the 5' UTR of RNA transcripts encoding several tryptophan metabolism genes, leading to their silencing. AT, whose expression is up-regulated upon tryptophan depletion to concentrations not exceeding a ratio of one AT trimer per TRAP 11-mer, restores tryptophan production by binding activated TRAP and preventing RNA binding. How the smaller AT inhibitor prevents RNA binding at such low stoichiometries has remained a puzzle, in part because of the large RNA-binding surface on the tryptophan-activated TRAP ring and its high affinity for RNA. Using X-ray scattering, hydrodynamic, and mass spectrometric data, we show that the polydentate action of AT trimers can condense multiple intact TRAP rings into large heterocomplexes, effectively reducing the available contiguous RNA-binding surfaces. This finding reveals an unprecedented mechanism for substoichiometric inhibition of a gene-regulatory protein, which may be a widespread but underappreciated regulatory mechanism in pathways that involve homo-oligomeric or polyvalent components.
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Affiliation(s)
- Elihu C. Ihms
- Department of Chemistry and Biochemistry
- Biophysics Graduate Program, and
| | - Mowei Zhou
- Department of Chemistry and Biochemistry
| | - Yun Zhang
- Department of Chemistry and Biochemistry
| | - Ian R. Kleckner
- Department of Chemistry and Biochemistry
- Biophysics Graduate Program, and
| | - Craig A. McElroy
- College of Pharmacy, The Ohio State University, Columbus, OH 43210; and
| | | | - Paul Gollnick
- Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY 14260
| | - Mark P. Foster
- Department of Chemistry and Biochemistry
- Biophysics Graduate Program, and
- Center for RNA Biology
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Zamora-Chimal C, Santillán M, Rodríguez-González J. Influence of the feedback loops in the trp operon of B. subtilis on the system dynamic response and noise amplitude. J Theor Biol 2012; 310:119-31. [PMID: 22713856 DOI: 10.1016/j.jtbi.2012.06.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 06/07/2012] [Accepted: 06/09/2012] [Indexed: 12/30/2022]
Abstract
In this paper we introduce a mathematical model for the tryptophan operon regulatory pathway in Bacillus subtilis. This model considers the transcription-attenuation, and the enzyme-inhibition regulatory mechanisms. Special attention is paid to the estimation of all the model parameters from reported experimental data. With the aid of this model we investigate, from a mathematical-modeling point of view, whether the existing multiplicity of regulatory feedback loops is advantageous in some sense, regarding the dynamic response and the biochemical noise in the system. The tryptophan operon dynamic behavior is studied by means of deterministic numeric simulations, while the biochemical noise is analyzed with the aid of stochastic simulations. The model feasibility is tested comparing its stochastic and deterministic results with experimental reports. Our results for the wildtype and for a couple of mutant bacterial strains suggest that the enzyme-inhibition feedback loop, dynamically accelerates the operon response, and plays a major role in the reduction of biochemical noise. Also, the transcription-attenuation feedback loop makes the trp operon sensitive to changes in the endogenous tryptophan level, and increases the amplitude of the biochemical noise.
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Affiliation(s)
- Criseida Zamora-Chimal
- Centro de Investigación y de Estudios Avanzados del IPN, Unidad Monterrey, Vía del Conocimiento 201, Parque de Investigación e Innovación Tecnológica, 66600 Apodaca NL, Mexico
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Mechanism for pH-dependent gene regulation by amino-terminus-mediated homooligomerization of Bacillus subtilis anti-trp RNA-binding attenuation protein. Proc Natl Acad Sci U S A 2010; 107:15385-90. [PMID: 20713740 DOI: 10.1073/pnas.1004981107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Anti-TRAP (AT) is a small zinc-binding protein that regulates tryptophan biosynthesis in Bacillus subtilis by binding to tryptophan-bound trp RNA-binding attenuation protein (TRAP), thereby preventing it from binding RNA, and allowing transcription and translation of the trpEDCFBA operon. Crystallographic and sedimentation studies have shown that AT can homooligomerize to form a dodecamer, AT(12), composed of a tetramer of trimers, AT(3). Structural and biochemical studies suggest that only trimeric AT is active for binding to TRAP. Our chromatographic and spectroscopic data revealed that a large fraction of recombinantly overexpressed AT retains the N-formyl group (fAT), presumably due to incomplete N-formyl-methionine processing by peptide deformylase. Hydrodynamic parameters from NMR relaxation and diffusion measurements showed that fAT is exclusively trimeric (AT(3)), while (deformylated) AT exhibits slow exchange between both trimeric and dodecameric forms. We examined this equilibrium using NMR spectroscopy and found that oligomerization of active AT(3) to form inactive AT(12) is linked to protonation of the amino terminus. Global analysis of the pH dependence of the trimer-dodecamer equilibrium revealed a near physiological pK(a) for the N-terminal amine of AT and yielded a pH-dependent oligomerization equilibrium constant. Estimates of excluded volume effects due to molecular crowding suggest the oligomerization equilibrium may be physiologically important. Because deprotonation favors "active" trimeric AT and protonation favors "inactive" dodecameric AT, our findings illuminate a possible mechanism for sensing and responding to changes in cellular pH.
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Shevtsov MB, Chen Y, Isupov MN, Leech A, Gollnick P, Antson AA. Bacillus licheniformis Anti-TRAP can assemble into two types of dodecameric particles with the same symmetry but inverted orientation of trimers. J Struct Biol 2010; 170:127-33. [PMID: 20138150 PMCID: PMC2896485 DOI: 10.1016/j.jsb.2010.01.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Revised: 01/21/2010] [Accepted: 01/23/2010] [Indexed: 01/07/2023]
Abstract
Anti-TRAP (AT) protein regulates expression of tryptophan biosynthetic genes by binding to the trp RNA-binding attenuation protein (TRAP) and preventing its interaction with RNA. Bacillus subtilis AT forms trimers that can either interact with TRAP or can further assemble into dodecameric particles. To determine which oligomeric forms are preserved in AT proteins of other Bacilli we studied Bacillus licheniformis AT which shares 66% sequence identity with the B. subtilis protein. We show that in solution B. licheniformis AT forms stable trimers. In crystals, depending on pH, such trimers assemble into two different types of dodecameric particles, both having 23 point group symmetry. The dodecamer formed at pH 6.0 has the same conformation as previously observed for B. subtilis AT. This dodecamer contains a large internal chamber with the volume of approximately 700 A(3), which is lined by the side chains of twelve valine residues. The presence of the hydrophobic chamber hints at the possibility that the dodecamer formation could be induced by binding of a ligand. Interestingly, in the dodecamer formed at pH 8.0 all trimers are turned inside out relatively to the form observed at pH 6.0.
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Affiliation(s)
- Mikhail B. Shevtsov
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO1 5YW, UK
| | - Yanling Chen
- Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY 14260, USA
| | - Michail N. Isupov
- School of Biosciences, Henry Wellcome Building for Biocatalysis, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
| | - Andrew Leech
- Department of Biology, University of York, Heslington, York YO1 5DD, UK
| | - Paul Gollnick
- Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY 14260, USA
| | - Alfred A. Antson
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO1 5YW, UK,Corresponding author. Fax: +44 1904 328266.
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Positions of Trp codons in the leader peptide-coding region of the at operon influence anti-trap synthesis and trp operon expression in Bacillus licheniformis. J Bacteriol 2010; 192:1518-26. [PMID: 20061467 DOI: 10.1128/jb.01420-09] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tryptophan, phenylalanine, tyrosine, and several other metabolites are all synthesized from a common precursor, chorismic acid. Since tryptophan is a product of an energetically expensive biosynthetic pathway, bacteria have developed sensing mechanisms to downregulate synthesis of the enzymes of tryptophan formation when synthesis of the amino acid is not needed. In Bacillus subtilis and some other Gram-positive bacteria, trp operon expression is regulated by two proteins, TRAP (the tryptophan-activated RNA binding protein) and AT (the anti-TRAP protein). TRAP is activated by bound tryptophan, and AT synthesis is increased upon accumulation of uncharged tRNA(Trp). Tryptophan-activated TRAP binds to trp operon leader RNA, generating a terminator structure that promotes transcription termination. AT binds to tryptophan-activated TRAP, inhibiting its RNA binding ability. In B. subtilis, AT synthesis is upregulated both transcriptionally and translationally in response to the accumulation of uncharged tRNA(Trp). In this paper, we focus on explaining the differences in organization and regulatory functions of the at operon's leader peptide-coding region, rtpLP, of B. subtilis and Bacillus licheniformis. Our objective was to correlate the greater growth sensitivity of B. licheniformis to tryptophan starvation with the spacing of the three Trp codons in its at operon leader peptide-coding region. Our findings suggest that the Trp codon location in rtpLP of B. licheniformis is designed to allow a mild charged-tRNA(Trp) deficiency to expose the Shine-Dalgarno sequence and start codon for the AT protein, leading to increased AT synthesis.
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Abstract
Tryptophan biosynthesis is subject to exquisite control in species of Bacillus and has become one of the best-studied model systems in gene regulation. The protein TRAP (trp RNA-binding attenuation protein) predominantly forms a ring-shaped 11-mer, which binds cognate RNA in the presence of tryptophan to suppress expression of the trp operon. TRAP is itself regulated by the protein Anti-TRAP, which binds to TRAP and prevents RNA binding. To date, the nature of this interaction has proved elusive. Here, we describe mass spectrometry and analytical centrifugation studies of the complex, and 2 crystal structures of the TRAP-Anti-TRAP complex. These crystal structures, both refined to 3.2-A resolution, show that Anti-TRAP binds to TRAP as a trimer, sterically blocking RNA binding. Mass spectrometry shows that 11-mer TRAP may bind up to 5 AT trimers, and an artificial 12-mer TRAP may bind 6. Both forms of TRAP make the same interactions with Anti-TRAP. Crystallization of wild-type TRAP with Anti-TRAP selectively pulls the 12-mer TRAP form out of solution, so the crystal structure of wild-type TRAP-Anti-TRAP complex reflects a minor species from a mixed population.
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McGraw AP, Mokdad A, Major F, Bevilacqua PC, Babitzke P. Molecular basis of TRAP-5'SL RNA interaction in the Bacillus subtilis trp operon transcription attenuation mechanism. RNA (NEW YORK, N.Y.) 2009; 15:55-66. [PMID: 19033375 PMCID: PMC2612762 DOI: 10.1261/rna.1314409] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Accepted: 10/14/2008] [Indexed: 05/27/2023]
Abstract
Expression of the Bacillus subtilis trpEDCFBA operon is regulated by the interaction of tryptophan-activated TRAP with 11 (G/U)AG trinucleotide repeats that lie in the leader region of the nascent trp transcript. Bound TRAP prevents folding of an antiterminator structure and favors formation of an overlapping intrinsic terminator hairpin upstream of the trp operon structural genes. A 5'-stem-loop (5'SL) structure that forms just upstream of the triplet repeat region increases the affinity of TRAP-trp RNA interaction, thereby increasing the efficiency of transcription termination. Single-stranded nucleotides in the internal loop and in the hairpin loop of the 5'SL are important for TRAP binding. We show here that altering the distance between these two loops suggests that G7, A8, and A9 from the internal loop and A19 and G20 from the hairpin loop constitute two structurally discrete TRAP-binding regions. Photochemical cross-linking experiments also show that the hairpin loop of the 5'SL is in close proximity to the flexible loop region of TRAP during TRAP-5'SL interaction. The dimensions of B. subtilis TRAP and of a three-dimensional model of the 5'SL generated using the MC-Sym and MC-Fold pipeline imply that the 5'SL binds the protein in an orientation where the helical axis of the 5'SL is perpendicular to the plane of TRAP. This interaction not only increases the affinity of TRAP-trp leader RNA interaction, but also orients the downstream triplet repeats for interaction with the 11 KKR motifs that lie on TRAP's perimeter, increasing the likelihood that TRAP will bind in time to promote termination.
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Affiliation(s)
- Adam P McGraw
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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