FIG. 1. Coq9p is peripherally associated to the inner mitochondrial membrane, facing toward the matrix side.
A) Mitochondria were subjected to hypotonic swelling and centrifugation to separate intermembrane space protein (IMS) and mitoplasts. The mitoplasts were either sonicated or treated with 0.1 M Na2CO3, pH 11.5, then separated via 100,000 × g centrifugation into pellet (P) or supernatant (S) fractions. B) Intact mitochondria or mitoplasts were treated with 100 μg/ml Proteinase K for 30 min on ice, in the presence or absence of detergent. Equal aliquots of pellets and TCA-precipitated soluble fractions were analyzed. Control polypeptide markers: (Atp2) β subunit of F1 ATPase, peripheral inner membrane; (Cyt b2) cytochrome b2, inter-membrane space; (Cyt c1) cytochrome c1, integral inner membrane; and (Hsp60), soluble matrix.