Yeast mitochondrial dehydrogenases are associated in a supramolecular complex

Separation of yeast mitochondrial complexes by colorless native polyacrylam ide gel electrophoresis led to the identification of a supramolecular struc ture exhibiting NADH-dehydrogenase activity. Components of this complex wer e identified by N-terminal Edman degradation and matrix-assisted laser deso rption ionization mass spectrometry. The complex was found to contain the f ive known intermembrane space-facing dehydrogenases, namely two external NA DH-dehydrogenases Nde1p and Nde2p, glycerol-3-phosphate dehydrogenase Gut2p , D- and L-lactate-dehydrogenases Dld1p and Cyb2p, the matrix-facing NADH-d ehydrogenase Ndi1p, two probable flavoproteins YOR356Wp and YPR004Cp, four tricarboxylic acids cycle enzymes (malate dehydrogenase Mdh1p, citrate synt hase Cit1p, succinate dehydrogenase Sdh1p, and famarate hydratase Fum1p), a nd the acetaldehyde dehydrogenase Ald4p. The association of these proteins is discussed in terms of NADH-channeling.