Identification of multiple ral gene products in human platelets that account for some but not all of the platelet G n-proteins

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Polyclonal antibodies raised against specific recombinant low molecular mass GTP-binding proteins were tested for their ability to recognize partially purified human platelet membrane G n-proteins (i.e. proteins that bind [α- 32PlGTP on nitrocellulose blots of SDS/polyacrylamide gels). An antiserum against simian ralA protein recognized a 27 kDa human platelet protein with the same apparent molecular mass as the major platelet G n-protein (G n27). In further analysis by two-dimensional polyacrylamide gel electrophoresis, the isoelectric focusing step permitted resolution of 12 major G n-protein forms, seven of 27 kDa (G n27a-g), one of 26 kDa (G n26) and four of 24 kDa (G n24a-d). The ralA antibody reacted strongly with the five most basic G n27 species (a-e), weakly with G n26 and not at all with G n27f, G n27g or G n24a-d. We conclude that ral gene products account for some but probably not for all of the platelet G n-proteins.