β-actin plasticity is modulated by coordinated actions of histidine 73 methylation, nucleotide type, and ions

Actin undergoes important structural changes to transition from the G-actin to the F-actin form. Furthermore, mammals express different isoforms, with only slight variations at the amino acid level. While the α-skeletal actin isoform was thoroughly studied using molecular dynamics simulations, the dynamics of the β-actin isoform remains unexplored. Here, we have used the AMOEBA polarizable force field coupled with adaptive sampling to investigate the plasticity of the β-actin. This highlighted the role of a post translational modification, i.e. the histidine 73 methylation, to enhance the opening of the actin cleft and change allosteric paths linking the two distant subdomains SD2 and SD4. The action of the methylation can be also modulated by the type of nucleotide bound in the actin cavity and the type of ions surrounding the protein. Taken together, these results shed new lights onto the plasticity of the β-actin isoform and the coordinated role of several environmental factors. These results may help designing new types of molecules, such as allosteric modulators, specifically targeting the β-actin isoform.