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J. Bacteriol., 07 1997, 4523-4529, Vol 179, No. 14
T Schiott, M Throne-Holst and L Hederstedt
Cytochromes of the c type contain covalently bound heme. In bacteria, they
are located on the outside of the cytoplasmic membrane. Cytochrome c
synthesis involves export of heme and apocytochrome across the cytoplasmic
membrane followed by ligation of heme to the polypeptide. Using radioactive
protoheme IX produced in Escherichia coli, we show that Bacillus subtilis
can use heme from the growth medium for cytochrome c synthesis. The B.
subtilis ccdA gene encodes a 26-kDa integral membrane protein which is
required for cytochrome c synthesis (T. Schiott et al., J. Bacteriol.
179:1962-1973, 1997). In this work, we analyzed the stage at which
cytochrome c synthesis is blocked in a ccdA deletion mutant. The following
steps were found to be normal in the mutant: (i) transcription and
translation of cytochrome c structural genes, (ii) translocation of
apocytochrome across the cytoplasmic membrane, and (iii) heme transport
from the cytoplasm to cytochrome polypeptide on the outer side of the
cytoplasmic membrane. It is concluded that CcdA is required for a late step
in the cytochrome c synthesis pathway.
Copyright © 1997, American Society for Microbiology
Bacillus subtilis CcdA-defective mutants are blocked in a late step of cytochrome c biogenesis
Department of Microbiology, Lund University, Sweden.
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