title: A COPI coat subunit interacts directly with an early-Golgi localized Arf exchange factor.
abstract: Arf (ADP-ribosylation factor) family small G proteins are crucial regulators of intracellular transport. The active GTP-bound form of Arf interacts with a set of proteins--effectors--which mediate the downstream signalling events of Arf activation. A well-studied class of Arf1 effectors comprises the coat complexes, such as the cis-Golgi-localized COPI (coat protein complex I) coat, and trans-Golgi network-endosomal clathrin coats. At least five different coats require Arf1-GTP to localize to organelle membranes. How a single Arf protein recruits different coat complexes to distinct membrane sites raises the question of how specificity is achieved. Here, we propose a molecular mechanism of this specificity for the COPI coat by showing a direct and specific interaction between a COPI subunit and a cis-Golgi localized subfamily of Arf guanine nucleotide exchange factors (GEFs) that takes place independently of Arf1 activation. In this way, a specific output on Arf1 activation can be programmed before the exchange reaction by the GEF itself.
authors.affiliation: Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Deng
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Golinelli-Cohen
authors.forename: Elena
authors.initials: E
authors.lastname: Smirnova
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Jackson
mesh_terms: D020823:ADP-Ribosylation Factor 1 / Q000378:metabolism*; D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism; D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology; D002460:Cell Line; D002522:Chlorocebus aethiops; D020755:Coat Protein Complex I / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D006056:Golgi Apparatus / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism; D006801:Humans; D011485:Protein Binding; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D020755:Coat Protein Complex I; C102475:GEA1 protein, S cerevisiae; C121632:GEA2 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D020126:Brefeldin A; D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors