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Originally published as Biophys J. BioFAST on August 17, 2007.
doi:10.1529/biophysj.107.109546
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Biophysical Journal 93:3783-3797 (2007)
© 2007 The Biophysical Society

How Directional Translocation is Regulated in a DNA Helicase Motor

Jin Yu * {dagger}, Taekjip Ha {dagger} {ddagger} and Klaus Schulten * {dagger}

* Beckman Institute; and {dagger} Department of Physics, University of Illinois at Urbana-Champaign, Champaign, Illinois; and {ddagger} Howard Hughes Medical Institute, Urbana, Illinois

Correspondence: Address reprint requests to Klaus Schulten, Beckman Institute, 405 N. Mathews, Urbana, IL 61801. Tel.: 217-244-1604; Fax: 217-244-6078; E-mail: kschulte{at}ks.uiuc.edu.

PcrA helicase from Bacillus stearothermophilus is one of the smallest motor proteins structurally known in full atomic detail. It translocates progressively from the 3' end to the 5' end of single-stranded DNA utilizing the free energy from ATP hydrolysis. The similarities in structure and reaction pathway between PcrA helicase and F1-ATPase suggest a similar mechanochemical mechanism at work in both systems. Previous studies of PcrA translocation demonstrated a domain stepping mechanism in which, during one ATP hydrolysis cycle, the pulling together and pushing apart of two translocation domains is synchronized with alternating mobilities of the individual domains such that PcrA moves unidirectionally along single-stranded DNA. To substantiate this translocation mechanism, this study applies molecular dynamics simulations, elastic network theory, and multiple sequence alignment to analyze the system. The analysis provides further evidence that directional translocation of PcrA is regulated allosterically through synchronization of ATP hydrolysis and domain mobilities. We identify a set of essential residues coevolutionarily coupled in related helicases that should be involved in the allosteric regulation of these motor proteins.






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Copyright © 2007 by the Biophysical Society.