Fig. 5. Conformational changes in p40 upon p70 complex formation optimize interactions with p35 R189. Internal conformational changes in D3 loops 5 and 6 are depicted as occurring after the D3 domain rotation described in Results. Overlay of unliganded p40 (gray) with p40 bound to p35 (turquoise) highlights movements of individual p40 side chains (arrows). Sixty-seven equivalent Cα atoms from the D3 domain of p40 and p70 were overlayed using lsqkab (CCP4, 1994) to an r.m.s.d. of 0.65 Å. Residues from loop 5 (240–249) and loop 6 (289–297) were excluded from the overlay.