Different Detergent Stability of ATP Synthase from Pea, Winter Wheat and Maize Mitochondria

Abstract

Mitochondrial ATP synthase is a macromolecular nanomachine, which produces most of the ATP in the cell. This enzyme is located in inner mitochondrial membrane in the form of dimers, which assemble into long rows at the cristae rims. Dimers of ATP synthase are sensitive to detergent treatment in many organisms, as a result of which they mainly dissociate into monomers. Plant enzyme is also very detergent-sensitive, nevertheless, it can be assumed that the detergent-sensitivity or, vice versa, detergent-stability of the enzyme under the treat-ment may vary in different plant species. In this regard, the aim of this work was to study the detergent-stability, as well as the activity of various forms of ATP synthase, solubilized from the mitochondria of different plant species. For this purpose, we used organelles isolated from etiolated pea, winter wheat, and maize shoots. These species belong to different families (Poaceae and Fabaceae), clades (monocots and dicots) and, in addition, differ in their low temperature tolerance. For the solubilization of organelles, a mild non-ionic detergent digitonin was used, which preserved and stabilized the supramolecular associations of membrane proteins. Using 1D BN-PAGE followed by ingel enzyme activity assay, it was shown that ATP synthase in all studied species was solubilized mainly as monomers Va and Vb, dimer Vb2, supercomplex IV1Va2, and minor subcomplex F1. In the course of the study, for the first time, differences in the detergent-stability of dimeric and monomeric forms of the enzyme between the studied species were revealed. It was found that the dimeric form in maize and the monomeric form in winter wheat were the most stable; while, pea ATP synthase had the highest activity. The relationship between the revealed features and the life strategy of the species is assumed and discussed.