Figure 5. DNA condensation by nanomolar ParB requires cytidine triphosphate (CTP) binding but not hydrolysis.

(A) Average force-extension curves of 13× parS DNA molecules in the presence of 2 mM CTPγS, 4 mM MgCl₂, and increasing concentrations of ParB. Results obtained with CTP (Figure 4D) and CTPγS were very similar. No ParB data represent force-extension curves of DNA taken in the absence of protein and are fitted to the worm-like chain model. Solid lines in condensed data are guides for the eye. Errors are standard error of the mean for measurements taken on different molecules (N ≥ 7). (B) Condensation assay of 13× parS DNA under 2 mM CTPγS and 1 mM EDTA conditions. DNA condensation by ParB and CTPγS requires Mg²⁺. (C) Condensation assay of 13× parS DNA under 2 mM cytidine diphosphate (CDP) and 4 mM MgCl₂ conditions.