Noncatalytic nucleotide binding sites: Properties and mechanism of involvement in ATP synthase activity regulation

Abstract

ATP synthases (FoF1-ATPases) of chloroplasts, mitochondria, and bacteria catalyze ATP synthesis or hydrolysis coupled with the transmembrane transfer of protons or sodium ions. Their activity is regulated through their reversible inactivation resulting from a decreased transmembrane potential difference. The inactivation is believed to conserve ATP previously synthesized under conditions of sufficient energy supply against unproductive hydrolysis. This review is focused on the mechanism of nucleotide-dependent regulation of the ATP synthase activity where the so-called noncatalytic nucleotide binding sites are involved. Properties of these sites varying upon free enzyme transition to its membrane-bound form, their dependence on membrane energization, and putative mechanisms of noncatalytic site-mediated regulation of the ATP synthase activity are discussed.

Reversible pH-dependent activation/inactivation of CF(1)-ATPase of spinach chloroplasts

“…The figures and the table show the mean values and their standard errors. At all pH values, the Ca 2+ -dependent ATPase activity at 26 °C was noticeably lower than the measurements made at 37 °C, that agrees with [2,5]. It should also be noted that Ca 2+ -ATPase activity of the isolated coupling factor CF 1 after preliminary incubation at low pH values (3.5, 4.5 or 5.4) was significantly inhibited compared to the control and at pH 7.8 both at 26 °C and at 37 °C.…”

“…After separation from the membrane, the catalytic part of the complex, the isolated coupling factor CF 1 , loses the ability to catalyse the ATP synthesis, but retains ATPase activity. In this case, the isolated CF 1 is a latent (hidden) ATPase and catalyses the hydroly sis of ATP only after activation by heat [5] or as a result of treatment with redox reagents, alcohols and some detergents [2]. A significant activation of ATP hydrolysis is also achieved when adding oxyanionbicarbonate, sulphite, phosphate, etc., to the reaction medium.…”

“…It was shown that the short-term incubation of isolated cF 1 ATP synthase (EC 3.6.3.14) is a membrane enzymatic complex which synthesis and hydrolysis of ATP coupled with the transmembrane proton transfer in chloroplasts, mitochondria and bacteria. It consists of a hydrophobic part F 0 , which functions as a proton channel and a hydrophilic part -a coupling factor F 1 , which contains several nucleotide binding sites and performs catalytic function [1,2]. Proton ATP synthases from various organisms have similar structure.…”

“…Proton ATP synthases from various organisms have similar structure. This is largely characteristic of chloroplast ATPase catalytic part -the CF 1 factor, which is water-soluble enzyme and consists of five types of polypeptides in stoichiometric ratio α:β:γ:δ:ε ~ 3:3:1:1:1 [2][3][4]. The central position of the ATP synthase complex in the energy supply of a living cell is determined by the need of precise regulation of its functioning and coordinated with the physiological state of an organism and its demand for energy.…”

“…A significant activation of ATP hydrolysis is also achieved when adding oxyanionbicarbonate, sulphite, phosphate, etc., to the reaction medium. [2,5,6].…”