title: Isolation and characterisation of a functional alpha beta heterodimer from the ATP synthase of Rhodospirillum rubrum.
abstract: An alpha beta heterodimer of the F1-ATPase of Rhodospirillum rubrum was isolated by extraction of chromatophores with LiCl. Each alpha beta heterodimer contains one tightly bound ADP, which is released upon removal of medium Mg2+. The dimer can be reversibly dissociated by removal of Mg(2+)-ions. The alpha beta heterodimer restores both ATP-synthetic and -hydrolytic activities to LiCl-treated chromatophores, saturation being achieved at approximately 2 mmol alpha beta.mol BChl-1. The heterodimer itself hydrolyses Mg-ATP with an activity distinct from RF1, being unaffected by azide or sulphite ions. The Vmax and Km (ATP) for this Mg(2+)-dependent activity were 110 +/- 10 nmol.min-1.mg protein-1 and 100 +/- 30 microM, respectively. The Km did not differ significantly from that of RF1.
authors.affiliation: Department of Biochemistry, University of Oxford, UK.
authors.forename: P J
authors.initials: PJ
authors.lastname: Andralojc
authors.forename: D A
authors.initials: DA
authors.lastname: Harris
mesh_terms: D000595:Amino Acid Sequence; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002712:Chlorides / Q000737:chemistry; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D008094:Lithium / Q000737:chemistry; D018021:Lithium Chloride; D008969:Molecular Sequence Data; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D012247:Rhodospirillum rubrum / Q000201:enzymology*
chemical_list: D002712:Chlorides; D008094:Lithium; D017301:Ca(2+) Mg(2+)-ATPase; D006180:Proton-Translocating ATPases; D018021:Lithium Chloride