Fine structural mapping of a critical NH2-terminal region of p60src.

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Abstract
An NH2-terminal sequence required for myristylation and membrane association of the Rous sarcoma virus transforming protein, p60src, was previously demonstrated to be contained with amino acids 2-14. This sequence is also required for cell transformation. Five mutants of Rous sarcoma virus that contain alterations in the src sequence coding for these 14 amino acids were constructed. Mutants encoding src proteins with a peptide insertion between amino acids 1 and 2, or peptide substitutions for amino acids 2-4, 3-4 or 7-15, were transformation-defective. The src proteins of these mutants differed from the wild-type protein in that they were not myristylated and did not fractionate with the palasma membrane of infected cells. The 5th mutant encoded a src protein with a short peptide substituted for amino acids 11-15. This protein was myristylated and plasma membrane associated, and the virus transformed cells. Thus, a sequence required for myristylation and membrane association of p60src is located within the first 7-10 amino acids of the src protein, and p60src myristylation and membrane association are required for cell transformation. Consistent with this idea, 4 transforming revertants were isolated from 1 of the transformation-defective mutants. The src proteins of all 4 revertants were found to be myristylated and membrane associated.