Fig. 5.

Proposed model of S. acidocaldarius branched aerobic respiratory chain. The respiratory chain model is based on separate biochemical characterization studies. Electrons from NADH or succinate oxidation presumably enter electron transport chain via NADH:quinone oxidoreductases or succinate:quinone oxidoreductases (not shown). Reduced quinones (CQH₂) then deliver electrons to cytochrome oxidase bc1 complex SoxLN-CbsAB-OdsN (42) and subsequently to one of the three terminal oxidase complexes. These terminal complexes are SoxABCD-SoxL (45, 54, 55), the bb3 terminal oxidase complex SoxEFGHIM (56–58), and the DoxBCE (59). Components whose transcript levels were altered in each deletion strain are depicted either in red or green for down- and up-regulation, respectively. Gene identifiers for each component are shown below.