Specificity of ParB proteins binding to parS sites in vitro, tested by competition with unlabeled DNA probes in gel mobility shift assays. (A and B) Specificity of the ParB proteins binding to cognate parS sites (ParBc-parSc and ParBm-parSm) tested by the addition of unlabeled competitor DNA probes. (C and D) Specificity of the ParB proteins binding to non-cognate parS sites (ParBc-parSm and ParBm-parSc) tested by the addition of unlabeled competitor DNA probes. The 25-bp DNA probes containing the wild-type and mutant parSc sequences are indicated as WT parSc and Mu parSc, and the 18-bp DNA probes containing the wild-type and mutant parSm sequences are indicated as WT parSm and Mu parSm. All reactions contained 15 pmol FAM-labeled wild-type parSc or parSm DNA probes, and purified ParBc or ParBm proteins were added with a concentration of either 0 (no protein) or 200 pmol.