MAGNESIUM REGULATES BOTH THE NUCLEOTIDE-BINDING AND THE ENZYME-ACTIVITY OF ISOLATED CHLOROPLAST COUPLING FACTOR-1

Citation
T. Hisabori et K. Mochizuki, MAGNESIUM REGULATES BOTH THE NUCLEOTIDE-BINDING AND THE ENZYME-ACTIVITY OF ISOLATED CHLOROPLAST COUPLING FACTOR-1, Journal of Biochemistry, 114(6), 1993, pp. 808-812
Citations number
25
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology
Journal title
ISSN journal
0021-924X
Volume
114
Issue
6
Year of publication
1993
Pages
808 - 812
Database
ISI
SICI code
0021-924X(1993)114:6<808:MRBTNA>2.0.ZU;2-N
Abstract
The inactivation and the activation of the ATPase of isolated CF1 as a ssayed by the hydrolysis of ATP in 10 s depended on prior binding of A DP-Mg and ATP-Mg. The effects of Mg2+ on the nucleotide binding kineti cs were studied by monitoring the time courses of UV spectral changes induced by the interaction between CF1 and ADP or ATP using a rapid-sc an spectrophotometer equipped with a stopped-flow cell. The apparent r ate constant of ADP binding to the two high-affinity sites on CF1 (des ignated sites B and C in the previous report [Hisabori, T. and Sakurai , H. (1984) Plant Cell Physiol. 25, 483-493]) was drastically increase d by prior binding of Mg2+ to CF1, but not ATP. The inhibitory effect of Mg2+ was attributed to a marked increase in k(on), for the inhibito ry ADP binding at the high-affinity sites induced by the previous bind ing of Mg2+ to the enzyme. The location of site B is suggested to be o n 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.