FIG. 4.

Interaction between B. anthracis and B. cereus PcrA helicases and RepC. The physical interaction between PcrA and RepC proteins was analyzed by a pull-down assay as described in the text. The eluted fractions from amylose resin columns (either containing [+] or lacking [−] bound MBP-RepC) were probed with either anti-MBP or anti-His₆ monoclonal antibodies (Ab). His-PcrA helicases from S. aureus (Sa), B. anthracis (Ba), and B. cereus (Bc) were used. Equal amounts of protein extracts containing His-PcrA were deposited in the load control lanes (Sa, Ba, and Bc load).The protein extracts were bound to a Ni-nitrilotriacetic acid column, eluted, and then analyzed by SDS-PAGE and immunoblotting. The same amounts of protein extracts were used in the pull-down assays. In lanes lacking MBP-RepC, 1% BSA was used instead.