Multiple cytochromes b in Mycobacterium phlei

Electron transport particles from $\text{M. phlei}$ contain at least 3 different active forms of cytochrome b, one reduced by NADH, with a λ_max at 563 nm (b_N563), and the other two reduced by either succinate or NADH, with λ_max at 559 and 563 nm (b_S559) and (b_S563). Low temperature λ_max for cytochrome b reduction with NADH or succinate are described. During steady state only b_S563 was observed with succinate. In the presence of ATP, succinate reduced an increased amount of a b563. A branching of the NAD⁺-linked pathway and a convergence at the level of cytochrome c is suggested, with only one branch accessible to succinate.