| Abstract: | The covalent binding of dialdehyde derivatives of ATP and ADP (o-ATP and o-ADP) results in inactivation of chloroplast CF1-ATPase, the degree of inactivation being increased at a rise in temperature and pH. o-ADP causes predominant inhibition of the Mg2+-dependent, while o-ATP--of both Mg2+- and Ca2+-dependent activities of CF1-ATPase. The substrates and reaction products prevent the enzyme inactivation, whereas the stimulators of the Mg2+-dependent ATPase activity enhance it. The effect of these stimulators is correlated with predominant incorporation of 3H] o-nucleotide into the beta-subunit of CF1. In the absence of the stimulators o-ADP is predominantly bound to the alpha-subunit of CF1. The binding of o-ADP and o-ATP to the beta-subunit is increased in the presence of Mg2+. A comparative analysis of the labelled nucleotides incorporation into individual subunits and the changes in the catalytic and regulatory properties of the enzyme demonstrated that the catalytic and stimulator-sensitive "regulatory" sites of the enzyme are located on the beta-subunits. |
