HIGH INFORMATION-CONSERVATION IMPLIES THAT AT LEAST 3 PROTEINS BIND INDEPENDENTLY TO F-PLASMID INCD REPEATS

The 12 incD repeats in the F plasmid each contain about 60 bits of information, which is three times the amount of conservation that a single protein would need to distinguish the repeats from the rest of the Escherichia coli genome. This is the first reported discovery of a case of threefold excess information, and it implies that at least three proteins bind independently to the repeats. In support of this observation, other workers have shown that three polypeptides bind to this region, but only one, SopB, is known to bind independently of other factors. Identification of the other two proteins should help us to understand the mechanism of plasmid partitioning during cell division.