PMID:9914305
| Citation |
Fabianek, RA, Hofer, T and Thöny-Meyer, L (1999) Characterization of the Escherichia coli CcmH protein reveals new insights into the redox pathway required for cytochrome c maturation. Arch. Microbiol. 171:92-100 |
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| Abstract |
The CcmH protein of Escherichia coli is encoded by the last gene of the ccm gene cluster required for cytochrome c maturation. A mutant in which the entire ccmH gene was deleted failed to synthesize both indigenous and foreign c-type cytochromes. However, deletion of the C-terminal hydrophilic domain homologous to CycH of other gram-negative bacteria affected neither the biogenesis of indigenous c-type cytochromes nor that of the Bradyrhizobium japonicum cytochrome c550. This confirmed that only the N-terminal domain containing a conserved CXXC motif is required in E. coli. PhoA fusion analysis showed that this domain is periplasmic. Site-directed mutagenesis of the cysteines of the CXXC motif revealed that both cysteines are required for cytochrome c maturation during aerobic growth, whereas only the second cysteine is required for cytochrome c maturation during anaerobic growth. The deficiency of the point mutants was complemented when 2-mercapto-ethanesulfonic acid was added to growing cells; other thiol compounds did not stimulate cytochrome c formation in these strains. We propose a model for the reaction sequence in which CcmH keeps the heme binding site of apocytochrome c in a reduced form for subsequent heme ligation. |
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| Keywords |
Bacterial Proteins/chemistry; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Cell Fractionation; Cysteine; Cytochrome c Group/genetics; Cytochrome c Group/metabolism; Escherichia coli/genetics; Escherichia coli/metabolism; Gene Deletion; Genes, Bacterial; Oxidation-Reduction; Phenotype; Plasmids; Point Mutation; Serine; Toluene/analogs & derivatives; Toluene/metabolism |
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