Crystal structure of the Escherichia coli regulator of sigma70, Rsd, in complex with sigma70 domain 4.
The Escherichia coli Rsd protein binds tightly and specifically to the RNA polymerase (RNAP) sigma(70) factor. Rsd plays a role in alternative sigma factor-dependent transcription by biasing the competition between sigma(70) and alternative sigma factors for the available core RNAP. Here, we determined the 2.6 A-resolution X-ray crystal structure of Rsd bound to sigma(70) domain 4 (sigma(70)(4)), the primary determinant for Rsd binding within sigma(70). The structure reveals that Rsd binding interferes with the two primary functions of sigma(70)(4), core RNAP binding and promoter -35 element binding. Interestingly, the most highly conserved Rsd residues form a network of interactions through the middle of the Rsd structure that connect the sigma(70)(4)-binding surface with three cavities exposed on distant surfaces of Rsd, suggesting functional coupling between sigma(70)(4) binding and other binding surfaces of Rsd, either for other proteins or for as yet unknown small molecule effectors. These results provide a structural basis for understanding the role of Rsd, as well as its ortholog, AlgQ, a positive regulator of Pseudomonas aeruginosa virulence, in transcription regulation.
The Rockefeller University, Box 224, 1230 York Avenue, New York, NY 10065, USA.
Georgia A
GA
Patikoglou
Lars F
LF
Westblade
Elizabeth A
EA
Campbell
Valérie
V
Lamour
William J
WJ
Lane
Seth A
SA
Darst
D000595:Amino Acid Sequence; D017124:Conserved Sequence; D003460:Crystallization; D018360:Crystallography, X-Ray; D004269:DNA, Bacterial / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry*; D012808:Sigma Factor / Q000737:chemistry*; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism
C078876:AsiA protein, Enterobacteria phage T4; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; C112239:Rsd protein, E coli; D012808:Sigma Factor; D014764:Viral Proteins; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases