title: Small molecular weight GTP-binding proteins in human erythrocyte ghosts.
abstract: GTP-binding proteins (G proteins) were extracted from human erythrocyte ghosts by sodium cholate and purified by gel filtration on an Ultrogel AcA-44 column followed by hydroxyapatite column chromatography. At least two peaks of G proteins were separated by hydroxyapatite column chromatography. The second peak contained G proteins recognized by the antibodies against the respective alpha subunits of Gs and Gi, and the ras protein, while the G protein of the first peak was not recognized by any of these antibodies. The G protein of the first peak was purified further by Mono Q HR5/5 column chromatography. The purified G protein showed a molecular weight of about 22 kDa on SDS-polyacrylamide gel electrophoresis. This G protein (22K G) specifically bound guanosine 5'-(3-O-thio) triphosphate (GTP gamma S), GTP and GDP with a Kd value for GTP gamma S of about 50 nM. GTP gamma S-binding to 22K G was inhibited by pretreatment with N-ethylmaleimide. The G proteins recognized by the antibodies against the alpha subunit of Go and the ADP-ribosylation factor for Gs, designated as ARF, were not detected in human erythrocyte ghosts. These results indicate that there are at least two species of small molecular weight G proteins in human erythrocyte ghosts: one is the ras protein and the other is a novel G protein of 22K G.
mesh_terms: D019826:Cholic Acid; D002793:Cholic Acids; D002845:Chromatography; D002850:Chromatography, Gel; D004229:Dithiothreitol / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000097:blood*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D013873:Thionucleotides / Q000378:metabolism
chemical_list: D002793:Cholic Acids; D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D019826:Cholic Acid; D005033:Ethylmaleimide; D004229:Dithiothreitol