Possible binding proteins of ras p21 in human erythrocyte membrane

The direct binding protein(s) of ras p21 was investigated in the inside-out vesicles of human erythrocyte ghosts using the pure v-Kirsten (Ki)-ras p21 synthesized in E. coli. The bound ras p21 was detected immunochemically using an anti-v-Ki-ras p21 monoclonal antibody. ras p21 was overlaid on the vesicle proteins immobilized on a nitrocellulose sheet transferred from the gel of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. ras p21 bound to bands 4.2 and 6. ras p21-binding to bands 4.2 and 6 was reduced by prior incubation of ras p21 with the purified band 4.2 or 6 protein. Furthermore, when ras p21 was mixed with inside-out vesicles and then centrifuged, ras p21 was coprecipitated with the vesicles. Prior digestion of the vesicles with trypsin reduced this binding significantly. These results indicate that v-Ki-ras p21 can bind directly to bands 4.2 and 6 of human erythrocyte membranes as fat as tested in an in vitro cell-free system.