LexA and lambda Cl repressors as enzymes: specific cleavage in an intermolecular reaction.
During the SOS response, LexA repressor is inactivated by specific cleavage. Although cleavage requires RecA protein in vivo, RecA acts indirectly as a coprotease by stimulating an inherent self-cleavage activity of LexA. In lambda lysogens, cleavage of lambda Cl repressor in a similar but far slower reaction results in prophage induction. We describe an intermolecular cleavage reaction in which the C-terminal fragment of LexA acted as an enzyme to cleave other molecules of LexA. The C-terminal fragment of lambda repressor cleaved the LexA substrates about as efficiently as did the LexA enzyme, suggesting that the slow rate of Cl self-cleavage results from a weak interaction between its cleavage site and the active site.
Department of Biochemistry, University of Arizona, Tucson 85721.
B
B
Kim
J W
JW
Little
D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D004268:DNA-Binding Proteins; D004789:Enzyme Activation; D004798:Enzymes / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D011938:Rec A Recombinases / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D012697:Serine Endopeptidases; D013379:Substrate Specificity; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D004798:Enzymes; D011938:Rec A Recombinases; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; D000099160:LexA Repressor Protein; C016649:phage repressor proteins