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Bacillus subtilis CtaA and CtaB function in haem A biosynthesis
B Svensson1, M Lübben, L Hederstedt
1Department of Microbiology, Lund University, Sweden.
Molecular Microbiology
|October 1, 1993
Summary
Bacillus subtilis CtaA and CtaB proteins are crucial for synthesizing heme A, a vital component of respiratory oxidases. Studies in E. coli and B. subtilis confirm their roles in heme A production.
Area of Science:
- Microbiology
- Biochemistry
- Molecular Biology
Background:
- Heme A is an essential prosthetic group for respiratory oxidases.
- Heme A synthesis likely proceeds from heme B (protoheme IX) via heme O.
- The specific roles of Bacillus subtilis ctaA and ctaB genes in this pathway were unclear.
Purpose of the Study:
- To investigate the functions of the Bacillus subtilis ctaA and ctaB gene products in heme O and heme A synthesis.
- To elucidate the roles of CtaA and CtaB in the heme A biosynthetic pathway.
Main Methods:
- Gene expression studies using plasmids in Escherichia coli.
- Construction and analysis of Bacillus subtilis ctaA and ctaB deletion mutants.
- Analysis of heme content (heme A, heme B, heme O) in wild-type and mutant strains.
Main Results:
- Expression of ctaA in E. coli led to heme A accumulation in membranes.
- Co-expression of ctaA and ctaB in E. coli further increased heme A levels.
- B. subtilis ctaA deletion mutants accumulated heme B and heme O but lacked heme A.
- B. subtilis ctaB deletion mutants lacked both heme A and heme O.
- Heme O was not detected in wild-type B. subtilis.
Conclusions:
- The B. subtilis CtaA protein is essential for heme A synthesis, potentially by oxygenating/oxidizing heme O.
- The B. subtilis CtaB protein also plays a critical role in heme A synthesis and is required for both cytochrome a and cytochrome o synthesis.