title: A mammalian guanine-nucleotide-releasing protein enhances function of yeast secretory protein Sec4.
abstract: Small GTP-binding proteins of the ras superfamily are important for exocytosis from eukaryotic cells. GTP-binding proteins can exist in two different conformations depending on whether they are bound to GDP or GTP, and are thought to function as molecular switches that regulate a variety of cellular processes. The GTP-GDP cycle is controlled by accessory proteins that promote the exchange of bound GDP or the hydrolysis of GTP. The protein Sec4, a member of the Sec4/Ypt1/Rab branch of the Ras superfamily, is involved in a late stage of the secretory pathway in yeast. Here we report the isolation of a mammalian complementary DNA, mss4, encoding a GDP-releasing protein that enhances Sec4 function. The Mss4 protein also stimulates GDP release from Ypt1 and from the mammalian protein Rab3a, but not from Ras2. Mss4 shows sequence similarity to Dss4, a yeast protein with similar biochemical properties.
authors.affiliation: Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510.
authors.forename: J
authors.initials: J
authors.lastname: Burton
authors.forename: D
authors.initials: D
authors.lastname: Roberts
authors.forename: M
authors.initials: M
authors.lastname: Montaldi
authors.forename: P
authors.initials: P
authors.lastname: Novick
authors.forename: P
authors.initials: P
authors.lastname: De Camilli
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D001923:Brain Chemistry; D002352:Carrier Proteins / Q000235:genetics / Q000494:pharmacology; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D019204:GTP-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D020691:rab GTP-Binding Proteins
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D020662:Guanine Nucleotide Exchange Factors; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D011506:Proteins; D012333:RNA, Messenger; C079550:Rabif protein, rat; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C461599:maltose transport system, E coli; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D004247:DNA; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C489795:MSS4 protein, S cerevisiae; D019204:GTP-Binding Proteins; C064320:SEC4 protein, S cerevisiae; D020691:rab GTP-Binding Proteins