A bacterial cytochrome c heme lyase - CcmF forms a complex with the heme chaperone CcmE and CcmH but not with apocytochrome c
Institute of Microbiology, ETH Zurich, Zürich, Zurich, Switzerland Journal of Biological Chemistry
(Impact Factor: 4.57).
04/2002; 277(10):7657-63. DOI: 10.1074/jbc.M110979200
Biogenesis of c-type cytochromes in Escherichia coli involves a number of membrane proteins (CcmA-H), which are required for the transfer of heme to the periplasmically located apocytochrome c. The pathway includes (i) covalent, transient binding of heme to the periplasmic domain of the heme chaperone CcmE; (ii) the subsequent release of heme; and (iii) transfer and covalent attachment of heme to apocytochrome c. Here, we report that CcmF is a key player in the late steps of cytochrome c maturation. We demonstrate that the conserved histidines His-173, His-261, His-303, and His-491 and the tryptophan-rich signature motif of the CcmF protein family are functionally required. Co-immunoprecipitation experiments revealed that CcmF interacts directly with the heme donor CcmE and with CcmH but not with apocytochrome c. We propose that CcmFH forms a bacterial heme lyase complex for the transfer of heme from CcmE to apocytochrome c.
Available from: PubMed Central
- "Both the thiol-disulfide exchange mechanisms depicted in Figure 6 suggest that CcmH is the direct reductant of the apoCytc disulfide; however, even if immunoprecipitation experiments failed to detect the formation of a mixed-disulfide complex between apoCyt and CcmH proteins , some in vitro evidence supporting the formation of such a complex has been presented. In particular, it has been shown that Rhodobacter capsulatus and Arabidopsis thaliana CcmH homologues (Rc-CcmH and At-CcmH) are able to reduce the CXXCH motif of an apoCyt-mimicking peptide [75, 96]. "
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ABSTRACT: Cytochromes c (Cyt c) are ubiquitous heme-containing proteins, mainly involved in electron transfer processes, whose structure and functions have been and still are intensely studied. Surprisingly, our understanding of the molecular mechanism whereby the heme group is covalently attached to the apoprotein (apoCyt) in the cell is still largely unknown. This posttranslational process, known as Cyt c biogenesis or Cyt c maturation, ensures the stereospecific formation of the thioether bonds between the heme vinyl groups and the cysteine thiols of the apoCyt heme binding motif. To accomplish this task, prokaryotic and eukaryotic cells have evolved distinctive protein machineries composed of different proteins. In this review, the structural and functional properties of the main maturation apparatuses found in gram-negative and gram-positive bacteria and in the mitochondria of eukaryotic cells will be presented, dissecting the Cyt c maturation process into three functional steps: (i) heme translocation and delivery, (ii) apoCyt thioreductive pathway, and (iii) apoCyt chaperoning and heme ligation. Moreover, current hypotheses and open questions about the molecular mechanisms of each of the three steps will be discussed, with special attention to System I, the maturation apparatus found in gram-negative bacteria.
Available from: Brion Duffy
- ")] and heme lyase [ccmF, ccmH (Ren et al., 2000)] involved in heme uptake during synthesis of c-type cytochromes which are synthesized under anaerobic conditions (Iobbi-Nivol et al., 1994). Other genes involved in iron uptake such as iroC encoding an ABC transporter that exports the siderophore enterobactin (Crouch et al., 2008), febA (SENTW_ 2865) encoding an TonBdependent outer membrane ferric enterobactin receptor Fig. 3. Representative gene clusters of genes with higher transcription in presence of sprouts compared with M9-glucose medium. "
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ABSTRACT: Sprouted seeds represent a great risk for infection by human enteric pathogens because of favourable growth conditions for pathogens during their germination. The aim of this study was to identify mechanisms of interactions of Salmonella enterica subsp. enterica Weltevreden with alfalfa sprouts. RNA-seq analysis of S. Weltevreden grown with sprouts in comparison with M9-glucose medium showed that among a total of 4158 annotated coding sequences, 177 genes (4.3%) and 345 genes (8.3%) were transcribed at higher levels with sprouts and in minimal medium respectively. Genes that were higher transcribed with sprouts are coding for proteins involved in mechanisms known to be important for attachment, motility and biofilm formation. Besides gene expression required for phenotypic adaption, genes involved in sulphate acquisition were higher transcribed, suggesting that the surface on alfalfa sprouts may be poor in sulphate. Genes encoding structural and effector proteins of Salmonella pathogenicity island 2, involved in survival within macrophages during infection of animal tissue, were higher transcribed with sprouts possibly as a response to environmental conditions. This study provides insight on additional mechanisms that may be important for pathogen interactions with sprouts.
Available from: Martin John Woodward
- "The genes ccmB, ccmC and ccmD convey the heme-b group to the product of CcmE, a monotopic membrane protein . The products of ccmF, ccmG and ccmH complex with CcmE to convey the heme-b group to the apocytochrome-c precursor of cytochrome-C [24,25]. Though these genes are ubiquitous amongst Gram negative bacteria, strains of E. coli have been discovered that lack the ccm operon and yet are able to synthesis cytochrome-c containing heme-b . "
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Despite the frequent isolation of Salmonella enterica sub. enterica serovars Derby and Mbandaka from livestock in the UK and USA little is known about the biological processes maintaining their prevalence. Statistics for Salmonella isolations from livestock production in the UK show that S. Derby is most commonly associated with pigs and turkeys and S. Mbandaka with cattle and chickens. Here we compare the first sequenced genomes of S. Derby and S. Mbandaka as a basis for further analysis of the potential host adaptations that contribute to their distinct host species distributions.
Comparative functional genomics using the RAST annotation system showed that predominantly mechanisms that relate to metabolite utilisation, in vivo and ex vivo persistence and pathogenesis distinguish S. Derby from S. Mbandaka. Alignment of the genome nucleotide sequences of S. Derby D1 and D2 and S. Mbandaka M1 and M2 with Salmonella pathogenicity islands (SPI) identified unique complements of genes associated with host adaptation. We also describe a new genomic island with a putative role in pathogenesis, SPI-23. SPI-23 is present in several S. enterica serovars, including S. Agona, S. Dublin and S. Gallinarum, it is absent in its entirety from S. Mbandaka.
We discovered a new 37 Kb genomic island, SPI-23, in the chromosome sequence of S. Derby, encoding 42 ORFS, ten of which are putative TTSS effector proteins. We infer from full-genome synonymous SNP analysis that these two serovars diverged, between 182kya and 625kya coinciding with the divergence of domestic pigs. The differences between the genomes of these serovars suggest they have been exposed to different stresses including, phage, transposons and prolonged externalisation. The two serovars possess distinct complements of metabolic genes; many of which cluster into pathways for catabolism of carbon sources.
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