title: Magnesium regulates both the nucleotide binding and the enzyme activity of isolated chloroplast coupling factor 1.
abstract: The inactivation and the activation of the ATPase of isolated CF1 as assayed by the hydrolysis of ATP in 10 s depended on prior binding of ADP-Mg and ATP-Mg. The effects of Mg2+ on the nucleotide binding kinetics were studied by monitoring the time courses of UV spectral changes induced by the interaction between CF1 and ADP or ATP using a rapid-scan spectrophotometer equipped with a stopped-flow cell. The apparent rate constant of ADP binding to the two high-affinity sites on CF1 (designated sites B and C in the previous report [Hisabori, T. & Sakurai, H. (1984) Plant Cell Physiol. 25, 483-493]) was drastically increased by prior binding of Mg2+ to CF1, but not ATP. The inhibitory effect of Mg2+ was attributed to a marked increase in kon for the inhibitory ADP binding at the high-affinity sites induced by the previous binding of Mg2+ to the enzyme. The location of site B is suggested to be on the beta subunit based on the difference spectral change induced by binding of the ADP analog 2',3'-O-(2,4,6-trinitrophenyl)ADP to CF1.
authors.affiliation: Department of Biology, Yokohama City University, Kanagawa.
authors.forename: T
authors.initials: T
authors.lastname: Hisabori
authors.forename: K
authors.initials: K
authors.lastname: Mochizuki
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism* / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000187:drug effects; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D002736:Chloroplasts / Q000737:chemistry / Q000187:drug effects* / Q000201:enzymology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D010944:Plants / Q000201:enzymology / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000187:drug effects* / Q000302:isolation & purification
chemical_list: D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases; D008274:Magnesium