TCB Publications - Abstract

Jin Yu, Taekjip Ha, and Klaus Schulten. How directional translocation is regulated in a DNA helicase motor. Biophysical Journal, 93:3783-3797, 2007. (PMC: 2084242)

YU2007 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 ssDNA utilizing the free energy from ATP hydrolysis. The similarities of 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 ssDNA. To substantiate this translocation mechanism, the present study applies molecular dynamics simulations, elastic network theory, and multiple sequence alignment to analyze the system. The analyses provide further evidence for directional translocation of PcrA being regulated allosterically through synchronization of ATP hydrolysis and domain mobilities. A set of essential residues coevolutionarily coupled in related helicases are identi ed that should be involved in the allosteric regulation of these motor proteins.

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