PcrA Helicase, a Molecular Motor Studied from the Electronic to the Functional Level

Abstract

Molecular motors are adenosine tri-phosphate (ATP) hydrolysis-driven, cellular proteins responsible for a wide variety of different tasks, such as transport, energy metabolism, and DNA processing. Their operation cycle spans a wide range of length and time scales, from the localized and fast chemical reaction in the catalytic site(s) to the large scale and much slower conformational motions involved in the motors' physiological function. From a computational point of view, this means that currently there exists no single approach capable of capturing the whole spectrum of events during molecular motor function. In the present review, we show for PcrA helicase, a molecular motor involved in the unwinding of double-stranded DNA, how a combination of computational approaches can be used to examine PcrA's function in its entirety as well as in detail. Combined quantum mechanical/molecular mechanical simulations are used to study the catalytic ATP hydrolysis event and its coupling to protein conformational changes. Molecular dynamics simulations then provide a means of studying overall PcrA function on a nanosecond time scale. Finally, to reach physiologically relevant time scales, i.e., milliseconds, stochastic simulations are employed. We show that by combining the three stated approaches one can obtain insight into PcrA helicase function.