Mechanism of helicase translocation along nucleic acid

TL;DR

This paper presents a model explaining helicase and ribosome translocation along nucleic acids, highlighting the roles of active and passive processes influenced by external force and translocation factor concentrations.

Contribution

It introduces a stochastic model incorporating active and passive translocation processes with sub-processes, providing insights into how external forces and factors affect translocation rates.

Findings

Translocation rate increases with external force.

High external force favors active process translocation.

Translocation is governed by mechanochemical sub-processes at high factor concentrations.

Abstract

In cells, helicase translocation along nucleic acid is essential for many biological processes. However, so far, the mechanism of this translocation is not fully understood. Recent studies show that helicase might translocate through two processes, active process and passive process, with different translocation rate. In this study, a model including such two processes is presented. In which, each of these two processes consists of two sub-processes, chemical sub-process in which needed translocation factors are attached, and mechanochemical sub-process in which helicase makes a forward translocation step. Helicase can switch stochastically between these two processes with external force dependent rates. By this model, ribosome translocation along message RNA is detailed discussed. We found that, with the increase of external force, the mean translocation rate of ribosome increases from one lower limit to one upper limit, and both of these two limits increase with concentrations of the translocation factors. Under high external force, ribosome translocates mainly through active process. At saturating concentrations of translocation factors, the translocation is governed by mechanochemical sub-processes.