A novel Rab6-interacting domain defines a family of Golgi-targeted coiled-coil proteins.
In recent years, a large number of coiled-coil proteins localised to the Golgi apparatus have been identified using antisera from human patients with a variety of autoimmune conditions [1]. Because of their common method of discovery and extensive regions of coiled-coil, they have been classified as a family of proteins, the golgins [1]. This family includes golgin-230/245/256, golgin-97, GM130/golgin-95, golgin-160/MEA-2/GCP170, giantin/macrogolgin and a related group of proteins - possibly splice variants - GCP372 and GCP364[2][3][4][5][6][7][8][9][10][11]. GM130 and giantin have been shown to function in the p115-mediated docking of vesicles with Golgi cisternae [12]. In this process, p115, another coiled-coil protein, is though to bind to giantin on vesicles and to GM130 on cisternae, thus acting as a tether holding the two together [12] [13]. Apart from giantin and GM130, none of the golgins has yet been assigned a function in the Golgi apparatus. In order to obtain clues as to the functions of the golgins, the targeting to the Golgi apparatus of two members of this family, golgin-230/245/256 and golgin-97, was investigated. Each of these proteins was shown to target to the Golgi apparatus through a carboxy-terminal domain containing a conserved tyrosine residue, which was critical for targeting. The domain preferentially bound to Rab6 on protein blots, and mutations that abolished Golgi targeting resulted in a loss of this interaction. Sequence analysis revealed that a family of coiled-coil proteins from mammals, worms and yeast contain this domain at their carboxyl termini. One of these proteins, yeast Imh1p, has previously been shown to have a tight genetic interaction with Rab6 [14]. On the basis of these data, it is proposed that this family of coiled-coil proteins functions in Rab6-regulated membrane-tethering events.
Barr
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IBLS, Division of Biochemistry and Molecular Biology, Davidson Building, University of Glasgow, Glasgow G12 8QQ, UK. f.barr@bio.gla.ac.uk
D000595:Amino Acid Sequence; D000818:Animals; D001324:Autoantigens / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D000077614:Golgi Matrix Proteins; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020691:rab GTP-Binding Proteins; D018631:ras Proteins / Q000378:metabolism*
D001324:Autoantigens; D002352:Carrier Proteins; C098772:GOLGA4 protein, human; C486294:Golga4 protein, mouse; D000077614:Golgi Matrix Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; C094135:Rab6 protein; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D020691:rab GTP-Binding Proteins; D018631:ras Proteins