Bacillus subtilis expresses two kinds of haem‐A‐containing terminal oxidases

Abstract

The expression of two different aa3‐type cytochrome oxidases is demonstrated in Bacillus subtilis. One of them (denoted caa3‐605), was predicted by DNA‐sequencing of Bacillus cytochrome oxidase genes, but has not been found previously. It contains covalently bound haem C in subunit II and is very similar to the enzyme previously described in the thermophilic bacterium PS3. The other oxidase (denoted aa3‐600) deviates from most known oxidases of aa3 type, and is probably identical with the oxidase described by de Vrij et al. [de Vrij, W., Azzi, A. & Konings, W. N. (1983) Eur. J. Biochem. 131, 97–103]. It shows no immunological cross‐reactivity to the PS3 enzyme and differs from this spectroscopically; it contains no CuA and does not oxidise cytochrome c despite of its haem‐A chromophores. It catalyses oxidation of quinols, which is proposed to be its physiological function. Copyright © 1991, Wiley Blackwell. All rights reserved