Fig. 6. Comparison of the recognition of the non-PxxP segments outside the conventional PxxP motifs. (A) Ribbon representation of the p47^phox tail peptide in complex with the p67^phox SH3(C). The residues directly contacting the helix–turn–helix structure (Ile374′ and Thr382′) are colored red, and the two α-helices are in green. The PxxP core proline residues (Pro363′ and Pro366′) are shown in yellow. (B) Ribbon representation of the PEP-3BP1 peptide in complex with the Csk SH3 (PDB entry 1JEG). The hydrophobic residues that are essential for the tight binding (Ile625 and Val626 in full-length PEP) are colored red, and the 3₁₀-helix is in cyan. The PxxP core proline residues (Pro614 and Pro617) are shown in yellow.