Cloning of the cta operon from alkaliphilic Bacillus firmus OF4 and characterization of the pH-regulated cytochrome caa3 oxidase it encodes.

摘要: We have cloned and sequenced the DNA of alkaliphilic Bacillus firmus OF4 encompassing cta operon that encodes a pH-regulated cytochrome caa3 oxidase. The gene organization is identical with homologous subtilis oxidase locus (van der Oost, J., von Wachenfeld, C., Hederstedt, L. & Saraste, M. (1991) Mol. Microbiol. 5, 2063-2072). deduced amino acid sequences four putative structural subunits (CtaC-F) indicate substantial similarity to caa3-type oxidases from other species members family mitochondrial-type aa3 oxidases. A marked paucity basic residues was noted in c-containing domain CtaC, which faces highly alkaline external milieu. also purified enzyme as three-subunit complex, possible trace amounts fourth subunit. N-terminal sequence analysis two largest confirmed them be encoded by genes. An additional, minor component distinctive chromatographic properties during purification. Analysis mRNA ctaD probe revealed an abundant 4-kilobase message right size encode CtaC-F. cellular content this varied growth pH. Cells grown at pH 10.5 contained 2 2.5 times more than those 7.5, good correspondence relative found cells. ctaB gene, immediately upstream ctaC-F genes, transcribed onto low abundance 5-kilobase message, likely Levels were not affected