A human exchange factor for ARF contains Sec7- and pleckstrin-homology domains.
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.
Chardin
P
P
Institut de Pharmacologie Moléculaire et Cellulaire du CNRS, Valbonne,France. chardin@unice.fr
Paris
S
S
Antonny
B
B
Robineau
S
S
Béraud-Dufour
S
S
Jackson
C L
CL
Chabre
M
M
D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors; D000595:Amino Acid Sequence; D001798:Blood Proteins / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli; D005656:Fungal Proteins / Q000737:chemistry* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010750:Phosphoproteins; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid
D001798:Blood Proteins; D005656:Fungal Proteins; C102475:GEA1 protein, S cerevisiae; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D007295:Inositol Phosphates; D010750:Phosphoproteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C066755:Sec7 guanine nucleotide exchange factors; C102474:cytohesin-2; C039077:platelet protein P47; D019204:GTP-Binding Proteins; D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors