Asymmetric mutations in the tetrameric R67 dihydrofolate reductase reveal high tolerance to active-site substitutions.

ABSTRACT: Type II R67 dihydrofolate reductase (DHFR) is a bacterial plasmid-encoded enzyme that is intrinsically resistant to the widely-administered antibiotic trimethoprim. R67 DHFR is genetically and structurally unrelated to E. coli chromosomal DHFR and has an unusual architecture, in that four identical protomers form a single symmetrical active site tunnel that allows only one substrate binding/catalytic event at any given time. As a result, substitution of an active-site residue has as many as four distinct consequences on catalysis, constituting an atypical model of enzyme evolution. Although we previously demonstrated that no single residue of the native active site is indispensable for function, library selection here revealed a strong bias toward maintenance of two native protomers per mu

SUBMITTER: Ebert MC 

PROVIDER: S-EPMC4380981 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature