Bacillus subtilis chytochrome oxidase mutants: biochemical analysis and genetic evidence for two aa3‐type oxidases

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Abstract
The ctaBCDEF genes coding for cytochrome c oxidase were found to reside adjacent to a regulatory gene ctaA at 127-degrees on the Bacillus subtilis chromosome. The structural genes for subunits I and II, ctaD and ctaC, were deleted by gene-replacement using a phleomycin-resistance marker. The mutant was unable to oxidize N,N,N',N'-tetramethyl-p-phenylenediamine and oxidized cytochrome c at a significantly lower rate. Absorption spectra of the mutant and wild-type membranes confirmed the presence of two haem A-containing enzymes in B. subtilis. Another mutant, with a spontaneous deletion upstream from ctaC, was found to express neither of these enzymes. Radioactive haem-labelling was used to identify subunit 11, which contains a haem C, and cytochrome c-550 among the membrane-bound c-type cytochromes of B. subtilis