IDENTIFICATION OF MITOCHONDRIAL RESPIRATO RY PROTEINS FROM THE GREEN-ALGA CHLAMYDOMONAS-REINHARDTII

Membrane preparations from the green alga Chlamydomonas reinhardtii co ntain both thylakoid and mitochondrial membranes[l]. These preparation s have been intensely used to study the structure, function and biogen esis of protein complexes involved in the photosynthetic pathway. We s how here that these preparations are also suitable for studying protei n complexes of the mitochondrial respiratory chain of the alga. The re spiratory complexes, fractionated on a sucrose gradient in the presenc e of Triton X-100, were identified by their catalytic properties and t heir polypeptide content. From the bottom to the top of the sucrose gr adient, we identified the NADH: ubiquinone oxidoreductase (complex I), the mitochondrial ATP synthase (FoF1-ATPase), the cytochrome bc(1) co mplex and the cytochrome c oxidase. At the top of the gradient, anothe r enzyme was detected which displayed an NADH:menaquinone oxidoreducta se activity.