title: N-terminal targeting of guanine nucleotide exchange factors (GEF) for ADP ribosylation factors (ARF) to the Golgi.
abstract: B2-1 (cytohesin-1) is a member of a group of proteins (including ARNO and ARNO3) that are all of similar size and domain composition. The three proteins contain an N-terminal coiled-coil domain, followed by a Sec7 and a pleckstrin homology (PH) domain. While it is well established that the Sec7 domain functions as a guanine nucleotide exchange factor (GEF) for ADP-ribosylation factors (ARFs) and the PH domain anchors the proteins to membrane phosphoinositols, the function of the N-terminal domain is unknown. Here we show that the N terminus of B2-1 (residues 1-54) is necessary and sufficient to target the protein to the Golgi. The Sec7+PH domains of B2-1 (residues 55-398) are not sufficient for Golgi localization. Further deletion analysis and point mutagenesis indicate that the coiled-coil domain within the N terminus is responsible for Golgi targeting. Furthermore, ARNO and ARNO3 N termini also have the same capability of targeting to the Golgi. We conclude that the N-terminal, (&agr;)-helical, coiled-coil domain is used to target this family of proteins to the Golgi complex.
authors.affiliation: Department of Biology, Dalhousie University, Halifax, Nova Scotia, B3H4J1, Canada.
authors.forename: S Y
authors.initials: SY
authors.lastname: Lee
authors.forename: B
authors.initials: B
authors.lastname: Pohajdak
mesh_terms: D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D019556:COS Cells; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D015815:Cell Adhesion Molecules; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; C100723:cytohesin-1; C102474:cytohesin-2; D020727:ADP-Ribosylation Factors