Figure 2.

Electron micrographs of protein-DNA complexes formed at the parC centromere-like site of plasmid R1 showing ParR binding (A and B), specific pairing of two DNA molecules (C–E) or a higher-order-complex containing multiple DNA molecules (F). ParR and/or ParM were incubated with the parC containing plasmid pMD330 and prepared for electron microscopy. The plasmid was linearized at a unique SspI site to generate a fragment in which the parC region is located asymmetrically. The linearization with SspI was performed either before or after addition of proteins as described below. Bar = 1 kb. (A) ParR bound to parC prepared by incubation of supercoiled pMD330 plasmid DNA with ParR and linearization after binding. (B) ParR bound to parC prepared by incubation of ParR with prelinearized pMD330 DNA. (C) Paired pMD330 plasmid molecules prepared by incubating supercoiled pMD330 with ParR followed by linearization. (D) Paired plasmid molecules prepared by incubating supercoiled pMD330 DNA with ParR, ParM, and ATP. (E) Paired pMD330 molecules formed with prelinearized DNA in the presence of ParR, ParM, and ATP. (F) Typical higher-order-complex where three or more parC DNA molecules are aggregated by ParR protein.