FIGURE 8.

Model for MukB-mediated DNA catenation. MukB (purple, hinge domain, stippled tubes, as coiled-coils, and orange, head domains) likely mediates catenation by bringing two molecules of gapped DNA close enough together that the probability increases when Topo III (green oval) gates on the ssDNA in the gap to pass a duplex segment from the other molecule of DNA through the gap. MukB is likely to bind two DNA molecules in the process, one via each head domain in the MukB dimer. Proximity of the DNA molecules might be achieved by either movement of the coiled-coil regions bringing the head domains closer together (top pathway) or perhaps intertwining of the coiled-coil regions might lead to intertwining of the two DNA molecules (bottom pathway). The model is discussed in the text.