A SINGLE-POINT MUTATION SWITCHES THE SPECIFICITY OF GROUP-III SRC HOMOLOGY (SH) 2 DOMAINS TO THAT OF GROUP-I SH2 DOMAINS

Src homology 2 (SH2) domains recognize phosphotyrosine-containing sequ ences, and thereby mediate the association of specific signaling prote ins in response to tyrosine phosphorylation (Pawson, T., and Schlessin ger, J. (1993) Curr. Biol. 3, 434-442). We have shown that specific bi nding of SH2 domains to tyrosine-phosphorylated sites is determined by sequences adjacent to the phosphotyrosine. Eased on the phosphopeptid e specific ity and crystal structures, SH2 domains were classified int o four different groups (Songyang, Z., Shoelson, S. E., Chaudhuri, M., Gish, G., Pawson, T., Haser, W. G., King, F., Roberts, T., Ratnofsky, S., Lechleider, R. J., Neel, E. G., R. E. E., Fajardo, J. E., Chou, M . M., Hanafusa, H., Schaffhausen, E., and Cantley, L. C. (1993) Cell 7 2, 767-778). The beta D5 residues of SH2 domains were predicted to be critical in distinguishing these groups (Songyang, Z., Shoelson, S. E. , Chaudhuri, M., Gish, G., Pawson, T., I-laser, W. G., King, F., Rober ts, T., Ratnofsky, S., Lechleider, R. J., Neel, E. G., R. E. E., Fajar do, J. E., Chou, M. Ri., Hanafusa, H., Schaffhausen, E., and Cantley, L. C. (1993) Cell 72, 767-778; Eck, M. J., Shoelson, S. E., and Harris on, S. C. (1993) Nature 362, 87-91). We report here that replacing the aliphatic residues at the beta D5 positions of two Group III SH2 doma ins (phosphoinositide 3-kinase N-terminal SH2 domain and phospholipase C-gamma C-terminal SH2 domain) with Tyr (as found in Group I SH2 doma ins) results in a switch in phosphopeptide selectivity, consistent wit h the specificities of Group I SH2 domains. These results establish th e importance of the beta D5 residue in determining specificities of SH 2 domains.