A human exchange factor for ARF contains Sec7- and pleckstrin-homology domains

• Published in: Nature (London) Vol. 384; no. 6608; pp. 481 - 484
• Main Authors: Chardin, Pierre, Paris, Sonia, Antonny, Bruno, Robineau, Sylviane, Béraud-Dufour, Sophie, Jackson, Catherine L, Chabre, Marc
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 05.12.1996; Nature Publishing Group
• Subjects: ADP-Ribosylation Factor 1; ADP-Ribosylation Factors; Amino Acid Sequence; Biological and medical sciences; Blood Proteins - chemistry; Blood Proteins - metabolism; Cell physiology; Escherichia coli; Fundamental and applied biological sciences. Psychology; Fungal Proteins - chemistry; Fungal Proteins - metabolism; GTP-Binding Proteins - chemistry; GTP-Binding Proteins - genetics; GTP-Binding Proteins - metabolism; GTPase-Activating Proteins; Guanine Nucleotide Exchange Factors; Humans; Inositol Phosphates - metabolism; Life Sciences; Membrane and intracellular transports; Molecular and cellular biology; Molecular Sequence Data; Mutagenesis; Phosphoproteins; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Saccharomyces cerevisiae Proteins; Sequence Homology, Amino Acid; Yeasts; Human; Intracellular transport; GTP; ADP ribosylation; Nucleotide sequence; Guanine nucleotide; Homology; Molecular interaction; Golgi apparatus; Binding protein; Complementary DNA; Gene; Domain structure; Molecular complex
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/384481a0

The small G protein ARF1 is involved in the coating of vesicles that bud from the Golgi compartments. Its activation is controlled by as-yet unidentified guanine-nucleotide exchange factors. Gea1, the first ARF exchange factor to be discovered in yeast, is a large protein containing a domain of homology with Sec7, another yeast protein that is also involved in secretion. Here we characterized a smaller human protein (relative molecular mass 47K) named ARNO, which contains a central Sec7 domain that promotes guanine-nucleotide exchange on ARF1. ARNO also contains an amino-terminal coiled-coil motif and a carboxy-terminal pleckstrin-homology (PH) domain. The PH domain mediates an enhancement of ARNO exchange activity by negatively charged phospholipid vesicles supplemented with phosphatidylinositol bisphosphate. The exchange activity of ARNO is not inhibited by brefeldin A, an agent known to block vesicular transport and inhibit the exchange activity on ARF1 in cell extracts. This suggests that a regulatory component which is sensitive to brefeldin A associates with ARNO in vivo, possibly through the amino-terminal coiled-coil. We propose that other proteins with a Sec7 domain regulate different members of the ARF family.