CHARACTERIZATION OF A MONOCLONAL-ANTIBODY RECOGNIZING THE E1-ALPHA SUBUNIT OF PLANT MITOCHONDRIAL PYRUVATE-DEHYDROGENASE

We have isolated a monoclonal antibody that recognizes the E1 alpha subunit of the plant mitochondrial pyruvate dehydrogenase complex. The antibody specifically recognizes the E1 alpha subunit from maize seedling, pea leaf, and castor oil seed endosperm mitochondrial pyruvate dehydrogenases, but does not recognize the E1 alpha subunit present in the plastid complexes from these plants. The pea mitochondrial pyruvate dehydrogenase complex was used for subsequent characterization of the antibody. Two-dimensional electrophoretic analysis of a phosphorylated pea mitochondrial pyruvate dehydrogenase complex preparation revealed that the monoclonal antibody recognizes ah phosphorylated forms of the E1 alpha subunit. Under these conditions, the only proteins recognized by the antibody are phosphorylated. Binding of the antibody to the pyruvate dehydrogenase complex inhibits both catalytic activity and phosphorylation of the E1 alpha subunit, but does not significantly inhibit dephosphorylation. The monoclonal antibody recognizes mitochondrial E1 alpha subunits from a variety of plant materials including monocot and dicot seedlings, and thermogenic and storage tissues. The antibody does not recognize the E1 alpha subunit from rat liver or pig heart mitochondria, yeast, or bacteria. This highly specific antibody will be a useful tool for study of plant mitochondrial pyruvate dehydrogenase complexes.