title: Crystal structure of the cytoplasmic N-terminal domain of subunit I, a homolog of subunit a, of V-ATPase.
abstract: Subunit "a" is associated with the membrane-bound (V(O)) complex of eukaryotic vacuolar H(+)-ATPase acidification machinery. It has also been shown recently to be involved in diverse membrane fusion/secretory functions independent of acidification. Here, we report the crystal structure of the N-terminal cytosolic domain from the Meiothermus ruber subunit "I" homolog of subunit a. The structure is composed of a curved long central α-helix bundle capped on both ends by two lobes with similar α/β architecture. Based on the structure, a reasonable model of its eukaryotic subunit a counterpart was obtained. The crystal structure and model fit well into reconstructions from electron microscopy of prokaryotic and eukaryotic vacuolar H(+)-ATPases, respectively, clarifying their orientations and interactions and revealing features that could enable subunit a to play a role in membrane fusion/secretion.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Sankaranarayanan
authors.initials: S
authors.lastname: Srinivasan
authors.forename: Nand K
authors.initials: NK
authors.lastname: Vyas
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Baker
authors.forename: Florante A
authors.initials: FA
authors.lastname: Quiocho
mesh_terms: D001665:Binding Sites; D002147:Calmodulin / Q000378:metabolism; D018360:Crystallography, X-Ray / Q000379:methods*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D050600:SNARE Proteins / Q000378:metabolism; D013824:Thermus / Q000201:enzymology; D025262:Vacuolar Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D021122:Protein Subunits; D050600:SNARE Proteins; D025262:Vacuolar Proton-Translocating ATPases