Purification and characterization of the mitochondrial F₁ ATPase from rice

Abstract

The mitochondrial F₁ ATPase from rice has been purified to homogeneity. One of the characteristic features of this ATPase is that it consists of six subunits of sizes 55 kDa (α + β ), 36 kDa (γ ), 26.2 kDa (δ '), 22 kDa (δ ) and 11 kDa (ε) unlike other monocot F₁ ATPases. It exhibits typical non-linear kinetics for ATP and can be stimulated by oxyanions like bicarbonate and sulphite. High concentrations of sulphite (> 10 mM) markedly inhibit the ATPase. Compared to maize F₁ ATPase, it has a relatively lower GTPase activity and completely lacks Ca²⁺ ATPase activity. However, in spite of the differences in the kinetic properties of the F₁ ATPases from rice and maize, no significant differences in the amino acid sequence of α and β subunits of rice and maize are observed except for three amino acid changes.