DNA Unwinding and Oligomerization Dynamics of Escherichia coli UvrD Helicase Revealed by Single-molecule Fluorescence Imaging

Abstract

The Escherichia coli UvrD protein is a superfamily 1, non-hexameric DNA helicase that plays a crucial role in repair mechanisms. Previous studies suggested that wild-type UvrD has optimal activity in its oligomeric form. Nevertheless, a conflicting monomer model was proposed using a UvrD mutant lacking the C-terminal 40 amino acids (UvrDΔ40C). Here, single-molecule direct visualization of UvrDΔ40C revealed that two or three UvrDΔ40C molecules were simultaneously involved in DNA unwinding, presumably in an oligomeric form, similar to that with wild-type UvrD. Thus, single-molecule direct visualization of nucleic acid-binding proteins provides quantitative and kinetic information to address their fundamental mechanisms.