A mutation at the dimer interface regulates catalysis

Fluoroacetate Dehalogenase (FAcD), a homodimeric dehalogenase of interest in bioremediation, displays half-of-the-sites reactivity, requiring allosteric communication between the subunits to coordinate the reaction. Dimer interfaces are an obvious site of interest for understanding communication between subunits and have been shown, in a variety of enzyme systems, to mediate such communication. However, mutations at these interfaces often need to be substantial to noticeably affect protein activity. In this study, we demonstrate that two subtle interface mutations of FAcD, either accelerate the reaction or results in near-complete loss of activity with structural evidence of disruption at the dimer interface. By examining these variants using ultrahigh-resolution crystallography and kinetics studies, the influence of dimer interface variations in hydrogen-bonding networks on enzyme activity can be elucidated.