A novel binding protein of the origin of the Escherichia coli chromosome.

The replication origin of Escherichia coli (oriC) was probed for specific binding proteins, using the gel shift assay. A 33-kDa protein that binds specifically to the right border of oriC, next to the rightmost of the binding sites of the initiator protein, DnaA, was identified and purified. The stoichiometry of protein to DNA is about 6 to 1. Around 5000 monomers of the protein, named Rob (right oriC binding), are present per cell. The rob gene has been located near 99.8 min on the E. coli map, cloned, and overexpressed. The total protein sequence reveals strong homologies to several regulatory proteins with which it shares the helix-turn-helix motif.