Figure 6. Working model of BsSMC loading and assembly into clusters.

(a) BsSMC associates with DNA and can undergo 1D diffusion. (b) Diffusing BsSMC molecules transiently localize likely due to bending or wrapping of DNA around their hinge/coiled-coil arms. (c) Cooperative interactions between BsSMC molecules, predominately on the same DNA strand, trap DNA loops. ATP stimulates these interactions while the presence of ScpAB attenuates cluster formation. (d) Repeated cycles of ATP hydrolysis resulting in opening of the ATPase head domains may enable the formation of a network of interacting BsSMC molecules.