The Escherichia coli Rsd protein binds tightly and specifically to<br />the RNA polymerase (RNAP) sigma(70) factor. Rsd plays a role in alternative<br />sigma factor-dependent transcription by biasing the competition between<br />sigma(70) and alternative sigma factors for the available core RNAP.<br />Here, we determined the 2.6 A-resolution X-ray crystal structure<br />of Rsd bound to sigma(70) domain 4 (sigma(70)(4)), the primary determinant<br />for Rsd binding within sigma(70). The structure reveals that Rsd<br />binding interferes with the two primary functions of sigma(70)(4),<br />core RNAP binding and promoter -35 element binding. Interestingly,<br />the most highly conserved Rsd residues form a network of interactions<br />through the middle of the Rsd structure that connect the sigma(70)(4)-binding<br />surface with three cavities exposed on distant surfaces of Rsd, suggesting<br />functional coupling between sigma(70)(4) binding and other binding<br />surfaces of Rsd, either for other proteins or for as yet unknown<br />small molecule effectors. These results provide a structural basis<br />for understanding the role of Rsd, as well as its ortholog, AlgQ,<br />a positive regulator of Pseudomonas aeruginosa virulence, in transcription<br />regulation.
Seia, Z., Musso, L., Palazzini, S., & Bertero, M. (2012). Skin Biopsy Procedures: How and Where to Perform a Proper Biopsy. In Skin Biopsy - Perspectives. InTech. https://doi.org/10.5772/25276