Diffusion of nucleotide excision repair protein XPA along DNA by coarse-grained molecular simulations

Protein XPA plays critical roles in nucleotide excision repair pathway. Recent experimental work showed that the functional dynamics of XPA involves the one-dimensional diffusion along DNA to search the damage site. Here, we investigate the involved dynamical process using extensive coarse-grained molecular simulations at various salt concentrations. The results demonstrated strong salt concentration dependence of the diffusion mechanisms. At low salt concentrations, the one-dimensional diffusion with rotational coupling is the dominant mechanism. At high salt concentrations, the diffusion by three-dimensional mechanism becomes more probable. At wide range of salt concentrations, the residues involved in the DNA binding are similar and the one-dimensional diffusion of XPA along DNA displays sub-diffusive feature. This sub-diffusive feature is tentatively attributed to diverse strengths of XPA-DNA interactions. In addition, we showed that both binding to DNA and increasing salt concentration tend to stretch the conformation of the XPA, which increases the exposure extent of the sites for the binding of other repair proteins.