title: Cooperativity among manganese-binding sites in the H+-ATPase of chloroplasts.
abstract: Coupling factor, isolated from lettuce chloroplasts, contained several binding sites for Mn2+ ions. Three of these sites showed strong cooperative interactions having a Hill coefficient of 2.9 +/- 0.20 and a Kd of 14.7 +/- 0.44 microM. Three additional non-interacting Mn2+-binding sites were found with a Kd of 46.7 +/- 2.3 microM. Chemical modification with naphthylglyoxal of 1 arginyl residue/chloroplast coupling factor 1, which inhibited ATPase activity, inhibited the cooperativity among the sites but did not prevent Mn2+ binding to the enzyme. It is suggested that the cooperative interaction among the Mn2+-binding sites is an expression of the interaction among the active sites of the enzyme which is required for catalysis.
authors.forename: R
authors.initials: R
authors.lastname: Hiller
authors.forename: C
authors.initials: C
authors.lastname: Carmeli
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000645:Ammonium Sulfate / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects; D002736:Chloroplasts / Q000201:enzymology*; D005990:Glycerol / Q000494:pharmacology; D006037:Glyoxal / Q000031:analogs & derivatives / Q000494:pharmacology; D008345:Manganese / Q000378:metabolism*; D010944:Plants / Q000201:enzymology; D006180:Proton-Translocating ATPases / Q000378:metabolism*
chemical_list: C044501:naphthylglyoxal; D008345:Manganese; D006037:Glyoxal; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D005990:Glycerol; D000645:Ammonium Sulfate