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

摘要: The extracytoplasmic function (ECF) sigma factor sigma(R) is a global regulator of redox homeostasis in the antibiotic-producing bacterium Streptomyces coelicolor, with similar role other actinomycetes such as Mycobacterium tuberculosis. Normally maintained an inactive state by its bound anti-sigma RsrA, dissociates response to intracellular disulphide-stress direct core RNA polymerase transcribe genes, trxBA and trxC that encode enzymes thioredoxin disulphide reductase pathway, re-establish homeostasis. Little known about where RsrA binds on or how it suppresses sigma(R)-dependent transcriptional activity. Using combination proteolysis, surface-enhanced laser desorption ionisation mass spectrometry pull-down assays we identify N-terminal, approximately 10kDa domain (sigma(RN)) encompasses region 2 represents major binding site. We show sigma(RN) inhibits transcription unrelated this inhibition relieved binding, reaffirming involved but also demonstrating likely mechanism which activity blocking association. report 2.4A resolution crystal structure reveals extensive structural conservation equivalent sigma(70) from Escherichia coli well cyclin-box, domain-fold found eukaryotic proteins TFIIB cyclin A. has propensity aggregate, due steric complementarity oppositely charged surfaces domain, inhibited observation suggests possible mode action for compare well-studied factor-anti-sigma systems.