1h3l
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(New page: 200px<br /><applet load="1h3l" size="450" color="white" frame="true" align="right" spinBox="true" caption="1h3l, resolution 2.375Å" /> '''N-TERMINAL FRAGMENT...)
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Revision as of 00:01, 25 November 2007
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N-TERMINAL FRAGMENT OF SIGR FROM STREPTOMYCES COELICOLOR
Overview
The extracytoplasmic function (ECF) sigma factor sigma(R) is a global, regulator of redox homeostasis in the antibiotic-producing bacterium, Streptomyces coelicolor, with a similar role in other actinomycetes such, as Mycobacterium tuberculosis. Normally maintained in an inactive state by, its bound anti-sigma factor RsrA, sigma(R) dissociates in response to, intracellular disulphide-stress to direct core RNA polymerase to, transcribe genes, such as trxBA and trxC that encode the enzymes of the, thioredoxin disulphide reductase pathway, that re-establish redox, homeostasis. Little is known about where RsrA binds on sigma(R) or how it, suppresses sigma(R)-dependent transcriptional activity. Using a, combination of proteolysis, surface-enhanced laser desorption ionisation, mass spectrometry and pull-down assays we identify an N-terminal, approximately 10kDa domain (sigma(RN)) that encompasses region 2 of, sigma(R) that represents the major RsrA binding site. We show that, sigma(RN) inhibits transcription by an unrelated sigma factor and that, this inhibition is relieved by RsrA binding, reaffirming that region 2 is, involved in binding to core RNA polymerase but also demonstrating that the, likely mechanism by which RsrA inhibits sigma(R) activity is by blocking, this association. We also report the 2.4A resolution crystal structure of, sigma(RN) that reveals extensive structural conservation with the, equivalent region of sigma(70) from Escherichia coli as well as with the, cyclin-box, a domain-fold found in the eukaryotic proteins TFIIB and, cyclin A. sigma(RN) has a propensity to aggregate, due to steric, complementarity of oppositely charged surfaces on the domain, but this is, inhibited by RsrA, an observation that suggests a possible mode of action, for RsrA which we compare to other well-studied sigma factor-anti-sigma, factor systems.
About this Structure
1H3L is a Single protein structure of sequence from Bacteria. Full crystallographic information is available from OCA.
Reference
Identification and structure of the anti-sigma factor-binding domain of the disulphide-stress regulated sigma factor sigma(R) from Streptomyces coelicolor., Li W, Stevenson CE, Burton N, Jakimowicz P, Paget MS, Buttner MJ, Lawson DM, Kleanthous C, J Mol Biol. 2002 Oct 18;323(2):225-36. PMID:12381317
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