Figure 5. Local structure and N_eq analyses.

N_eq values (average number of PBs weighted by their frequencies, see Materials and Methods) of residues from the PSI, I-EGF-1, and I-EGF-2 domains were computed for L33 (blue lines) and P33 (red lines) β3 forms. For each domain, the absolute value of N_eq L33 and N_eq P33 differences (ΔN_eq) is also plotted (black lines). The sequence of the C26–C38 loop in the PSI domain is highlighted (pink-shaded area). The horizontal gray lines indicate an N_eq value of 1. A N_eq value of 1 indicates strong structure rigidity since only one PB is adopted by the residue; above 1, flexibility is proportional to the N_eq value. N_eq analyses demonstrated that the three domain structures are highly flexible, in particular, PSI has four small interspersed rigid areas. L33 and P33 (indicated by an arrow), belong to a rigid stretch (residues 33 to 35). Residues whose ΔN_eq was significantly modified (see Materials and Methods) by the L33P substitution are identified by a vertical dotted line.