Fig. 4.

Predicted distribution of PR–PRE₂ ligation states in the presence of equimolar concentrations of both isoforms. Simulations were carried out by using the dimer pathway energetics and assume that (i) the A- and B-isoforms heterodimerize with an average of the two homodimerization affinities, (ii) heterodimers bind a PRE with an average of the PR-A and PR-B homodimer affinity, and (iii) intersite cooperativity occurring within DNA-induced heterotetramers is equal to the average of the intersite cooperativity within a PR-A or PR-B saturated PRE₂. Representative ligation states and the ratio of PR-A to PR-B in the PR–PRE₂ complex are indicated in the schematics.