title: ATP hydrolysis catalyzed by a beta subunit preparation purified from the chloroplast energy transducing complex CF1.CF0.
abstract: Washing thylakoid membranes with 1 M LiCl causes the release of the beta subunit from the chloroplast energy transducing complex (CF1.CF0) in spinach chloroplasts. This protein purifies by size exclusion chromatography as a 180-kDa aggregate and, thus, is probably composed of a trimer of beta polypeptides. The purified aggregate binds ADP to a high and a low affinity site with dissociation constants of 15 and 202 microM, respectively. Mg2+ is required for ADP to bind to both sites. Manganese binds to the protein in a cooperative manner to at least two sites with high affinity. The beta subunit preparation catalyzes Mg2+-dependent ATP hydrolysis at rates which are comparable to other subunit-deficient CF1 preparations and is increased by treatments known to activate the Mg2+-ATPase activity of CF1. However, Ca2+ is not an effective cofactor for this reaction and treatments which activate the Ca2+-ATPase of CF1 are either ineffective or inhibitory.
authors.affiliation: Department of Biology, University of Michigan, Ann Arbor 48109-1048.
authors.forename: W D
authors.initials: WD
authors.lastname: Frasch
authors.forename: J
authors.initials: J
authors.lastname: Green
authors.forename: J
authors.initials: J
authors.lastname: Caguiat
authors.forename: A
authors.initials: A
authors.lastname: Mejia
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D001665:Binding Sites; D015153:Blotting, Western; D002384:Catalysis; D002712:Chlorides; D002736:Chloroplasts / Q000201:enzymology*; D006868:Hydrolysis; D008094:Lithium; D018021:Lithium Chloride; D008274:Magnesium / Q000502:physiology; D008345:Manganese / Q000378:metabolism; D008970:Molecular Weight; D010940:Plant Proteins / Q000302:isolation & purification / Q000502:physiology*; D006180:Proton-Translocating ATPases / Q000378:metabolism*
chemical_list: D002712:Chlorides; D010940:Plant Proteins; D008345:Manganese; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D008094:Lithium; D006180:Proton-Translocating ATPases; D018021:Lithium Chloride; D008274:Magnesium