title: Escherichia coli ccm in-frame deletion mutants can produce periplasmic cytochrome b but not cytochrome c.
abstract: Escherichia coli CcmA, CcmB and CcmC polypeptides are required for cytochrome c synthesis and are thought to constitute the subunits of an ABC-type transporter as judged from sequence data. Using a periplasmic reporter system based on Bacillus subtilis cytochrome c-550 and E. coli cytochrome b-562 we show that the synthesis of the b-type cytochrome in the periplasm is normal in E. coli ccmA and ccmC in-frame deletion mutants. Mutants deleted for ccmF or ccmG encoding a component of a putative cytochrome c-heme lyase and a membrane bound thioredoxin-like protein, respectively, have the same phenotype. The ccm mutants produce cytochrome c-550 polypeptide, but not holocytochrome c. Taken together the results demonstrate that heme can be transported to the periplasm by a ccm-independent mechanism.
authors.affiliation: Department of Microbiology, Lund University, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Throne-Holst
authors.forename: L
authors.initials: L
authors.lastname: Thöny-Meyer
authors.forename: L
authors.initials: L
authors.lastname: Hederstedt
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis* / Q000235:genetics; D003573:Cytochrome b Group / Q000096:biosynthesis* / Q000235:genetics; D003574:Cytochrome c Group / Q000096:biosynthesis* / Q000235:genetics; D003593:Cytoplasm / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D017384:Sequence Deletion
chemical_list: D018528:ATP-Binding Cassette Transporters; C513740:CcmB protein, E coli; D003573:Cytochrome b Group; D003574:Cytochrome c Group