title: Heterogeneity of guanine nucleotide binding proteins in human red blood cell membranes.
abstract: Membranes from human erythrocytes bind radioactive GTP and GTP analogs according to apparently homogeneous patterns. In spite of this uniform type of association, multiple guanine nucleotide binding proteins have been identified both by SDS-PAGE analysis of native and of variously ADP-ribosylated membrane preparations and by FPLC chromatography of solubilised erythrocyte membranes preliminarily incubated with [alpha-32P] GTP in the presence of 5 mM MgCl2. From eight to nine peak fractions of pronase-digestible GTP-binding activity were separated on a MA7Q anion exchange column, this pattern being highly reproducible with different membrane preparations. Prior incubation of membranes with [alpha-32P] GTP in the presence of excess unlabeled GDP resulted in displacement of bound labeled nucleotide from all FPLC fractions. The patterns of GTP binding were also markedly modified by preliminary treatment of membranes with N-ethylmaleimide. Detectable GTPase activity was present in each of the FPLC peak fractions. This wide heterogeneity of guanine nucleotide binding proteins raises so far unanswered questions as to their physiological significance in the mature erythrocyte.
authors.affiliation: Institute of Biochemistry, University of Genoa, Italy.
authors.forename: A
authors.initials: A
authors.lastname: De Flora
authors.forename: G
authors.initials: G
authors.lastname: Damonte
authors.forename: A
authors.initials: A
authors.lastname: Sdraffa
authors.forename: L
authors.initials: L
authors.lastname: Franco
authors.forename: U
authors.initials: U
authors.lastname: Benatti
mesh_terms: D001797:Blood Protein Electrophoresis; D002845:Chromatography / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000737:chemistry*; D020558:GTP Phosphohydrolases / Q000302:isolation & purification*; D019204:GTP-Binding Proteins / Q000145:classification* / Q000302:isolation & purification; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D015398:Signal Transduction
chemical_list: D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins