Biochemical properties of p60v-src mutants that induce different cell transformation parameters

PA101 and PA104 are Rous sarcoma virus variants that are differentially temperature sensitive in cell transformation parameters, including stimulation of cell proliferation, morphological alteration, and anchorage independence. To investigate the biochemical basis for the differential expression of these parameters, the tyrosine kinase activity and subcellular localization of the mutant p60v-src proteins encoded in the variants were examined. Analysis of chimeric src proteins derived from the mutant proteins revealed that lesions in the kinase domain inhibit in vitro kinase activity and confer temperature sensitivity on tyrosine phosphorylation of cellular protein p34 in vivo. The amino-terminal portions of the mutant src proteins also influence tyrosine phosphorylation in vivo and in vitro, which is consistent with an interaction between an amino-terminal region and the kinase domain. Large proportions of the mutant src proteins exist in soluble complexes with cellular proteins p50 and p90, even though the src proteins are myristylated. The formation of these soluble complexes segregates with lesions in the kinase domain and is independent of temperature. Our results demonstrate that the transformation parameters examined correlate to a limited extent with p34 phosphorylation but not with the levels of in vitro kinase activity or soluble complex formation.