Mechanism of specific LexA cleavage: autodigestion and the role of RecA coprotease.
Specific LexA cleavage can occur under two different conditions: RecA-mediated cleavage requires an activated form of RecA, while an intramolecular self-cleavage termed autodigestion proceeds spontaneously at high pH and does not involve RecA. The two cleavage reactions are closely related. We postulate that RecA stimulates autodigestion rather than acting as a typical protease, and it is proposed to term this activity 'RecA coprotease' to emphasize this indirect role. The mechanism of autodigestion is similar to that of a serine protease, and RecA appears to act by reducing the pKa of a critical lysine residue LexA. A new class of mutants, termed lexA (IndS), is described; these mutations increase the rate of LexA cleavage.
Little
J W
JW
Department of Biochemistry, University of Arizona, Tucson 85721.
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D006868:Hydrolysis; D008969:Molecular Sequence Data; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D013014:SOS Response, Genetics; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein