title: Crystal structure of LexA: a conformational switch for regulation of self-cleavage.
abstract: LexA repressor undergoes a self-cleavage reaction. In vivo, this reaction requires an activated form of RecA, but it occurs spontaneously in vitro at high pH. Accordingly, LexA must both allow self-cleavage and yet prevent this reaction in the absence of a stimulus. We have solved the crystal structures of several mutant forms of LexA. Strikingly, two distinct conformations are observed, one compatible with cleavage, and the other in which the cleavage site is approximately 20 A from the catalytic center. Our analysis provides insight into the structural and energetic features that modulate the interconversion between these two forms and hence the rate of the self-cleavage reaction. We suggest RecA activates the self-cleavage of LexA and related proteins through selective stabilization of the cleavable conformation.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, 2146 Health Sciences Mall, Vancouver, British Columbia, V6T 1Z3, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Luo
authors.forename: R A
authors.initials: RA
authors.lastname: Pfuetzner
authors.forename: S
authors.initials: S
authors.lastname: Mosimann
authors.forename: M
authors.initials: M
authors.lastname: Paetzel
authors.forename: E A
authors.initials: EA
authors.lastname: Frey
authors.forename: M
authors.initials: M
authors.lastname: Cherney
authors.forename: B
authors.initials: B
authors.lastname: Kim
authors.forename: J W
authors.initials: JW
authors.lastname: Little
authors.forename: N C
authors.initials: NC
authors.lastname: Strynadka
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D001665:Binding Sites; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000235:genetics; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein