Identification and Structure of the Anti-sigma Factor-binding Domain of the Disulphide-stress Regulated Sigma Factor sR from Streptomyces coelicolor

Li, Wei, Stevenson, Clare E M, Burton, Nicolas, Jakimowicz, Piotr, Paget, Mark S B, Buttner, Mark J, Lawson, David M and Kleanthous, Colin (2002) Identification and Structure of the Anti-sigma Factor-binding Domain of the Disulphide-stress Regulated Sigma Factor sR from Streptomyces coelicolor. Journal of Molecular Biology, 323 (2). pp. 225-236. ISSN 0022-2836

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Abstract

The extracytoplasmic function (ECF) sigma factor sR 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, sR 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 sR or how it suppresses sR-dependent transcriptional activity. Using a combination of proteolysis, surface-enhanced laser desorption ionisation mass spectrometry and pull-down assays we identify an N-terminal, 10 kDa domain (sRN) that encompasses region 2 of sR that represents the major RsrA binding site. We show that sRN 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 sR activity is by blocking this association. We also report the 2.4 Å resolution crystal structure of sRN that reveals extensive structural conservation with the equivalent region of s70 from Escherichia coli as well as with the cyclin-box, a domain-fold found in the eukaryotic proteins TFIIB and cyclin A. sRN 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.

Item Type: Article
Schools and Departments: School of Life Sciences > Biochemistry
Depositing User: EPrints Services
Date Deposited: 06 Feb 2012 20:39
Last Modified: 22 Mar 2012 13:56
URI: http://sro.sussex.ac.uk/id/eprint/27307
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