Figure 5.
Schematic views of lac repressor (R) interacting with large operator-containing DNA molecules in dilute solution. The DNA molecules are shown well separated into domains. The (upper right) expanded view shows R bound to a segment of nonspecific DNA, on which it can slide or hop in one-dimensional processes or engage in three-dimensional association-dissociation reactions in seeking its specific (operator) target site. The (lower right) expanded view shows a repressor molecule doubly bound to two DNA segments, corresponding to an intermediate in the intersegment transfer process. Modified from Reference 80.