Specific association of activated MAP kinase kinase kinase (Raf) with the plasma membranes of ras-transformed retinal cells

Plasma membrane-enriched fractions were prepared from human embryonic retinal cells tranformed with either adenovirus E1A and oncogenic ras DNA, or E1A and E1B DNA. Ras comprised 5-10% of the membrane protein from the E1A/ras transformed cells, whereas the membranes from E1A/E1B transformed cells did not overexpress Ras. The membranes from E1A/ras cells. contained MAP kinase kinase kinase (MAPKKK) activity, even after washing in 0.5M NaCl, whereas the membranes from E1A/E1B cells did not. Neither membrane fractioncontained MAP kinase kinase or MAP kinase activity after washing with 0.5M NaCl