title: Membrane fusion by the GTPase atlastin requires a conserved C-terminal cytoplasmic tail and dimerization through the middle domain.
abstract: The biogenesis and maintenance of the endoplasmic reticulum (ER) requires membrane fusion. ER homotypic fusion is driven by the large GTPase atlastin. Domain analysis of atlastin shows that a conserved region of the C-terminal cytoplasmic tail is absolutely required for fusion activity. Atlastin in adjacent membranes must associate to bring the ER membranes into molecular contact. Drosophila atlastin dimerizes in the presence of GTPγS but is monomeric with GDP or without nucleotide. Oligomerization requires the juxtamembrane middle domain three-helix bundle, as does efficient GTPase activity. A soluble version of the N-terminal cytoplasmic domain that contains the GTPase domain and the middle domain three-helix bundle serves as a potent, concentration-dependent inhibitor of membrane fusion both in vitro and in vivo. However, atlastin domains lacking the middle domain are without effect. GTP-dependent dimerization of atlastin generates an enzymatically active protein that drives membrane fusion after nucleotide hydrolysis and conformational reorganization.
authors.affiliation: Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005, USA.
authors.forename: Tyler J
authors.initials: TJ
authors.lastname: Moss
authors.forename: Camilla
authors.initials: C
authors.lastname: Andreazza
authors.forename: Avani
authors.initials: A
authors.lastname: Verma
authors.forename: Andrea
authors.initials: A
authors.lastname: Daga
authors.forename: James A
authors.initials: JA
authors.lastname: McNew
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D017124:Conserved Sequence; D019281:Dimerization; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000502:physiology; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D006150:Guanine Nucleotides / Q000378:metabolism; D007700:Kinetics; D008561:Membrane Fusion / Q000502:physiology*; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid
chemical_list: D029721:Drosophila Proteins; D006150:Guanine Nucleotides; D011993:Recombinant Fusion Proteins; D020558:GTP Phosphohydrolases; C543694:atl protein, Drosophila