title: Differential cleavage of LexA and UmuD mediated by recA Pro67 mutants: implications for common LexA and UmuD binding sites on RecA.
abstract: In Escherichia coli, RecA-mediated cleavage of LexA repressor is a key regulatory event required for expression of SOS genes involved in the repair of DNA damage. RecA also mediates the cleavage of UmuD protein to UmuD, a form active in SOS mutagenesis. To determine whether LexA and UmuD have common binding determinants on RecA, we have compared the ability of several recA mutants to function in the cleavage of LexA versus UmuD in vivo. The data reveal that while some recA mutations at Pro67 have a similar effect on LexA and UmuD cleavage, others have striking differential effects. For example, a Pro67-->Trp mutation results in a high level of constitutive cleavage of both proteins. However, Pro67-->Asp and Glu mutations promote constitutive cleavage of LexA and reduce induction of UmuD cleavage to just 5 to 10% of wild-type activity. In contrast, Pro67-->Arg prevents LexA cleavage while allowing nearly 50% of wild-type induction of UmuD cleavage. These results are consistent with the idea that Pro67 is located at a site in the nucleoprotein filament where both LexA and UmuD contact RecA.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Massachusetts Medical Center, Worcester 01655, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Konola
authors.forename: A
authors.initials: A
authors.lastname: Guzzo
authors.forename: J B
authors.initials: JB
authors.lastname: Gow
authors.forename: G C
authors.initials: GC
authors.lastname: Walker
authors.forename: K L
authors.initials: KL
authors.lastname: Knight
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D004259:DNA-Directed DNA Polymerase; D029968:Escherichia coli Proteins; D008958:Models, Molecular; D009154:Mutation; D011392:Proline; D011487:Protein Conformation; D011938:Rec A Recombinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism*; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D004259:DNA-Directed DNA Polymerase; D029968:Escherichia coli Proteins; D011392:Proline; D011938:Rec A Recombinases; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein; C055218:UmuD protein, E coli