Figure 6.

Estimating fractional looping for different DNA distances. (A) Reporters with increased Oid-Plac.O2 spacings were made by integrating an 8 kb plasmid into the abc and b’ segments of reporter strains to make strains ID1318/ID1319 (abc: Oid^–/Oid⁺) and strains ID1320/ID1321 (b’: Oid^–/Oid⁺). F_L values (± 95% confidence limits, Student's t, n = 8) were measured as in Figure 4. (B) Plot of predicted fractional looping by the candidate protein, F_X, versus DNA distance, d (bp), for different values of I_L/I_X, using the relationships F = J/(J+I) (35) and J = 1.04 × 10⁶ × d^1.15 nM (36) and assuming I_L = 38.3 nM. Points are F_L looping values for LacI/Oid-O2 from Figure 5 and (A) and are reasonably fitted by the F_X curve for I_L/I_X = 1.