NMR analysis of the structure of Crk II and pCrkII. (A) NMR structure of CrkII (1–304) and phosphorylated form of CrkII (1–228). SH2, SH3N, and SH3C are indicated as red, green, and blue colors. Inter SH3 core region (224–237) of CRKII is indicated as yellow. In pCrkII, interface of SH3N is covered with the sequence between SH2 and SH3N (122-133 as magenta). Phosphorylated residue of pYAQP is indicated as light blue. (B). Schematic structure of CrkII with SH3N target C3G. In the cytoplasm, equilibrium of CrkII alone and CrkII/C3G complex may be established.