3vep
Crystal structure of SigD4 in complex with its negative regulator RsdA
Structural highlights
FunctionRSDA_MYCTU An anti-sigma factor for extracytoplasmic function (ECF) sigma factor SigD. ECF sigma factors are held in an inactive form by an anti-sigma factor until released by regulated intramembrane proteolysis (RIP). RIP occurs when an extracytoplasmic signal triggers a concerted proteolytic cascade to transmit information and elicit cellular responses. The membrane-spanning regulatory substrate protein is first cut extracytoplasmically (site-1 protease, S1P), then within the membrane itself (site-2 protease, S2P), while cytoplasmic proteases finish degrading the regulatory protein, liberating the sigma factor. Neither S1P nor S2P proteases have been so far identified for this anti-sigma factor. Publication Abstract from PubMedThe relative levels of different sigma factors dictate the expression profile of a bacterium. Extracytoplasmic function sigma factors synchronize the transcriptional profile with environmental conditions. The cellular concentration of free extracytoplasmic function sigma factors is regulated by the localization of this protein in a sigma/anti-sigma complex. Anti-sigma factors are multi-domain proteins with a receptor to sense environmental stimuli and a conserved anti-sigma domain (ASD) that binds a sigma factor. Here we describe the structure of Mycobacterium tuberculosis anti-sigma(D) (RsdA) in complex with the -35 promoter binding domain of sigma(D) (sigma(D)(4)). We note distinct conformational features that enable the release of sigma(D) by the selective proteolysis of the ASD in RsdA. The structural and biochemical features of the sigma(D)/RsdA complex provide a basis to reconcile diverse regulatory mechanisms that govern sigma/anti-sigma interactions despite high overall structural similarity. Multiple regulatory mechanisms embedded in an ASD scaffold thus provide an elegant route to rapidly re-engineer the expression profile of a bacterium in response to an environmental stimulus. Mycobacterium tuberculosis RsdA provides a conformational rationale for selective regulation of sigma-factor activity by proteolysis.,Jaiswal RK, Prabha TS, Manjeera G, Gopal B Nucleic Acids Res. 2013 Jan 11. PMID:23314154[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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