SMC complex unidirectionally translocates DNA by coupling segment capture with an asymmetric kleisin path
SMC (structural maintenance of chromosomes) protein complexes are ring-shaped molecular motors essential for genome folding. Despite recent progress, the detailed molecular mechanism of DNA translocation in concert with the ATP-driven conformational changes of the complex remains to be clarified. In this study, we elucidated the mechanisms of SMC action on DNA using multiscale molecular dynamics simulations. We first created a near-atomic full-length model of prokaryotic SMC-kleisin complex that implemented protein-DNA hydrogen bond interactions derived from fully atomistic simulations and emulated ATP-dependent conformational changes. Extensive simulations of the SMC complex with 800 base pairs of duplex DNA over the ATP cycle revealed unidirectional DNA translocation via the DNA segment capture mechanism. The process exhibited a step size of ~200 base pairs, wherein the complex captured a DNA segment of about the same size within the SMC ring in the engaged state, followed by its pum