title: Properties of the exchange rate of guanine nucleotides to the novel rap-2B protein.
abstract: Rap-2B is a novel ras-related protein that is 89% identical to rap-2 at the amino acid level. Based on its amino acid sequence, it is anticipated that rap-2B binds guanine nucleotides. Here we show that purified, bacterially expressed rap-2B does bind both GTP and GDP in a Mg2(+)-dependent fashion. The relative affinity of rap-2B for GTP is higher than that for GDP, both at low and high concentrations of Mg2+. This contrasts with N-ras p21 and could be of functional significance. Moreover, a polyclonal antiserum was raised against the recombinant rap-2B protein purified from E. coli lysates. This antiserum recognized a major protein of Mr approximately 21000 on Western blots of platelet membrane proteins, and immunoprecipitates rap-2B complexed with GTP or GDP.
authors.affiliation: Division of Cell Biology, Burroughs Wellcome Co., Research Triangle Park, NC 27709.
authors.forename: L
authors.initials: L
authors.lastname: Molina y Vedia
authors.forename: C A
authors.initials: CA
authors.lastname: Ohmstede
authors.forename: E G
authors.initials: EG
authors.lastname: Lapetina
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D001792:Blood Platelets / Q000201:enzymology*; D015153:Blotting, Western; D002462:Cell Membrane / Q000201:enzymology; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D006150:Guanine Nucleotides / Q000378:metabolism*; D006801:Humans; D008274:Magnesium / Q000378:metabolism; D008970:Molecular Weight; D011994:Recombinant Proteins; D020668:rap GTP-Binding Proteins
chemical_list: D000911:Antibodies, Monoclonal; D006150:Guanine Nucleotides; D011994:Recombinant Proteins; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; C065562:RAP2B protein, human; D020668:rap GTP-Binding Proteins; D008274:Magnesium