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Heme A synthase enzyme functions dissected by mutagenesis of Bacillus subtilis CtaA

Author

Summary, in English

Heme A, as a prosthetic group, is found exclusively in respiratory oxidases of mitochondria and aerobic bacteria. Bacillus subtilis CtaA and other heme A synthases catalyze the conversion of a methyl side group on heme 0 into a formyl group. The catalytic mechanism of heme A synthase is not understood, and little is known about the composition and structure of the enzyme. In this work, we have: (i) constructed a ctaA deletion mutant and a system for overproduction of mutant variants of the CtaA protein in B. subtilis, (ii) developed an affinity purification procedure for isolation of preparative amounts of CtaA, and (iii) investigated the functional roles of four invariant histidine residues in heme A synthase by in vivo and in vitro analyses of the properties of mutant variants of CtaA. Our results show an important function of three histidine residues for heme A synthase activity. Several of the purified mutant enzyme proteins contained tightly bound heme O. One variant also contained trapped hydroxylated heme 0, which is a postulated enzyme reaction intermediate. The findings indicate functional roles for the invariant histidine residues and provide strong evidence that the heme A synthase enzyme reaction includes two consecutive monooxygenations.

Publishing year

2005

Language

English

Pages

8361-8369

Publication/Series

Journal of Bacteriology

Volume

187

Issue

24

Document type

Journal article

Publisher

American Society for Microbiology

Topic

  • Microbiology

Status

Published

ISBN/ISSN/Other

  • ISSN: 0021-9193