Affiliation:
1. Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama 35294
Abstract
ABSTRACT
When a mutation in an essential gene shows a temperature-sensitive phenotype, one usually assumes that the protein is inactive at nonpermissive temperature. DNA gyrase is an essential bacterial enzyme composed of two subunits, GyrA and GyrB. The
gyrB652
mutation results from a single base change that substitutes a serine residue for arginine 436 (R436-S) in the GyrB protein. At 42°C, strains with the
gyrB652
allele stop DNA replication, and at 37°C, such strains grow but have RecA-dependent SOS induction and show constitutive RecBCD-dependent DNA degradation. Surprisingly, the GyrB652 protein is not inactive at 42°C in vivo or in vitro and it doesn't directly produce breaks in chromosomal DNA. Rather, this mutant has a low
k
cat
compared to wild-type GyrB subunit. With more than twice the normal mean number of supercoil domains, this gyrase hypomorph is prone to fork collapse and topological chaos near the terminus of DNA replication.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
18 articles.
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