Essential Structural Features and Orientation of Cytochrome b5 in Membranes

摘要: It is clear the cytochrome b 5 serves as a mobile electron carrier or shuttle to provide reducing equivalents for number of oxidation-reduction reactions that utilize cytoplasmically generated reduced pyridine nucleotides sources. Thus, two flavoproteins, NADH reductase (Spatz and Strittmatter, 1973) P-450 (Oshino et al., 1971; Enoch 1979a), reduce membrane-bound heure protein rapidly, former with turnover 30,000 min−1 at 30°C latter 7000 33°C (Enoch 1979a). Reduced direct donor stearyl-CoA desaturase (Δ9 fatty acyl CoA desaturase) (Holloway Wakil, 1970; Oshino Omura, 1973; Holloway Katz, 1972; Strittmatter 1974; 1976), may participate in reduction well (Hildebrandt Estabrook, Lau Saesame Imai Sato, 1977). In addition, microsomal has been implicated reductant Δ6 desaturation acids (Okayasu 1977; Lee 1977), cholesterol biosynthesis (Reddy plasmalogen (Paultanf 1974), more recently elongation (Keyes 1979). Both relatively large nonstoichiometric amount endoplasmic reticulum relative any one enzymes which it interacts, evidence interaction prepared phospholipid vesicles diffusion limited (Strittmatter Rogers, 1975; Rogers 1974) indicate translational movement heme within membrane bilayers crucial functional feature this carrier.