Structural highlights
Publication Abstract from PubMedIn many gamma-proteobacteria, the RpoS/sigmaS sigma factor associates with the core RNA polymerase (RNAP) to modify global gene transcription in stationary phase and under stress conditions. The small regulatory protein Crl stimulates the association of sigmaS with the core RNAP in Escherichia coli and Salmonella enterica serovarTyphimurium (S. Typhimurium), through direct and specific interaction with sigmaS. The structural determinants of Crl involved in sigmaS binding are unknown. Here, we report the X-ray crystal structure of the Proteus mirabilis Crl protein (CrlPM) and a structural model for S. Typhimurium Crl (CrlSTM). Using a combination of in vivo and in vitro assays, we demonstrated that CrlSTM and CrlPM are structurally similar and perform the same biological function. In the Crl structure, a cavity enclosed by flexible arms contains two patches of conserved and exposed residues required for sigmaS binding. Among these, charged residues likely to be involved in electrostatic interactions driving Crl-sigmaS complex formation were identified. CrlSTM and CrlPM interact with domain 2 of sigmaS with the same binding properties as with full-length sigmaS. These results suggest that Crl family members share a common mechanism of sigmaS binding in which the flexible arms of Crl might play a dynamic role. Structural and functional features of Crl proteins and identification of conserved surface residues required for interaction with the RpoS/sigmaS subunit of RNA polymerase.,Cavaliere P, Levi-Acobas F, Mayer C, Saul FA, England P, Weber P, Raynal B, Monteil V, Bellalou J, Haouz A, Norel F Biochem J. 2014 Jul 24. PMID:25056110[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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