Figure 3.

The ParB–DNA nucleoprotein complex recruits SMC to coordinate chromosome segregation and chromosome organization. (a) Components of the bacterial SMC complex. (b) SMC (grey) tethers the two arms (blue and orange) of a circular chromosome together. An SMC–ScpA–ScpB complex can either hold both the left and the right arm of the chromosome within its lumen or two SMC complexes, each encircles one chromosome arm, can handcuff to tether both chromosome arms together. For simplicity, only SMCs entrapping both chromosome arms are shown. SMC probably packages sister chromosomes into individual entities and away from each other, thus minimizing DNA entanglement between replicating chromosomes. (c) A schematic model of how SMC is loaded at parS by ParB and translocates on the chromosome towards the replication terminus (ter). For simplicity, alternative conformations of SMC (ring or rod) are not illustrated; the SMC complex is shown as a generic ring that entraps DNA. Schematic pictures are not drawn to scale.