HIGHLY CONSERVED AMINO-ACIDS IN THE SH2 AND CATALYTIC DOMAINS OF V-SRC ARE ALTERED IN NATURALLY-OCCURRING, TRANSFORMATION-DEFECTIVE ALLELES

We have identified 11 novel point mutations that abolish the transform ing capacity of the oncogene v-src. These transformation-defective all eles were originally identified in morphologically flat subclones of r at cells transformed by wild type v-src. Nine of the mutations affect amino acid residues that are highly conserved in the catalytic domain of pp60(v-src) and completely abolish kinase activity. The other 2 mut ations alter conserved residues in the SH2 domain (Phe-172 replaced wi th Val in one case [F172V] and Leu-186 replaced with Phe in the other [L186F]), drastically reducing, but not eliminating, kinase activity. The enzymatic and transforming functions of one of the SH2 mutants, L1 86F are host dependent; the mutant protein is active in chicken cells, but inactive in rat cells, as previously observed for some other SH2 mutants. These results are interpreted in relation to the recently des cribed three-dimensional structures of SH2 domains and of the catalyti c domain of a protein kinase. In addition, they support a role for the SH2 domain in the regulation of kinase activity.