G n-proteins are distinct from ras p21 and other known low molecular mass GTP-binding proteins in the platelet

Abstract

The 27 kDa platelet membrane protein (G n27) that binds [α- 32P]GTP on nitrocellulose blots of SDS-polyacrylamide gels [(1987) Biochem. J. 245, 617–620] was compared with other low molecular mass GTP-binding proteins. Platelet membranes also contained 21 kDa proteins that bound anti- ras p21 antibody and 22–23 kDa proteins that could be ADP-ribosylated by botulinum neurotoxin type D. These groups of proteins were resolved electrophoretically from each other and from G n27. A low molecular mass GTP-binding protein from bovine brain [(1987) Biochem. J. 246, 431–439] was also resolved from G n27. At the levels normally present in cell membranes, only G n-proteins bound significant amounts of [ 32P]GTP after transfer of protein from SDS-polyacrylamide gels to nitrocellulose.