Substrate identification with the yeast substrate-trapping system.
(A) Yeast proteins were highly tyrosine-phosphorylated
only when v-src was induced in the absence of methionine (−Met),
whereas almost no tyrosine-phosphorylation was observed in the presence
of methionine (+Met). Yeast lysates (70 μg) were analyzed by Western
blotting with antiphosphotyrosine antibody. (B)
β-Galactosidase filter-lift assay for clone 10–1. A filter placed on
the plate lacking leucine, tryptophan, and methionine
(Left) and lacking leucine and tryptophan
(Right) was streaked directly with clone 10–1 and
pBridgeLexA/ζICR-D1902A/v-src cotransformants, incubated at
30°C for 2 days, and developed for 3 h for color detection.
(C) The prey consisting of the GAL4 activation domain
fused to GIT1/Cat-1 was actually tyrosine-phosphorylated by v-src
induction (−Met). Yeast cell lysates (750 μg) were
immunoprecipitated with anti-GIT1/Cat-1 antiserum and analyzed by
Western blotting with antiphosphotyrosine antibody
(Upper) and anti-GIT1/Cat-1 antiserum
(Lower).