Figure 4.

Models for the contribution of TrfA to β-clamp loading at RK2 plasmid origin (oriV). We propose three model mechanisms for β-clamp loading at oriV through cooperated action of TrfA and clamp loader. (A) The first model suggests that ssDNA-bound TrfA recruits and hands off the β-clamp to clamp loader. (B) The second model implies that ssDNA-bound TrfA recruits the β-clamp in complex with clamp loader, thereby increasing the local concentration of β-clamp:clamp loader complex at oriV. (C) The third model indicates that TrfA binds β-clamp that is in complex with the clamp loader and directs it to the ssDNA of oriV.