Post-translational maturation of c-type cytochromes involves covalent attachment of haem to the apocytochrome polypeptide by two thioether bonds. In bacteria, haem attachment occurs in the periplasm, after the separate translocation of haem and the polypeptide across the cytoplasmic membrane. In Escherichia coli, delivery and attachment of the cofactor requires eight or nine specific proteins, which are believed to be organized in a membrane protein complex. After transport across the membrane, haem is attached covalently to the haem chaperone CcmE in an unusual way at a single histidine residue. However, haem binding to CcmE is transient and is succeeded by a further transfer to apocytochrome c. Both haem binding to and release from CcmE involve integral membrane proteins, CcmC and CcmF respectively, which carry a conserved tryptophan-rich motif in a periplasmic domain. Apocytochrome c polypeptides are synthesized as precursors and reach the periplasm by sec-dependent translocation. There they are prepared for haem binding by reduction of the cysteine residues in the motif Cys-Xaa-Xaa-Cys-His, which is characteristic of such proteins. This reduction is achieved in a thioreduction pathway, whereby electrons are passed from cytoplasmic thioredoxin to the transmembrane protein DsbD, across the membrane, and on to the specific reductases CcmG/CcmH. The merging of the haem delivery and the thioreduction pathways leads to the stereospecific insertion of haem into various type c cytochromes.
Skip Nav Destination
Article navigation
August 2002
-
Cover Image
Cover Image
- PDF Icon PDF LinkFront Matter
- PDF Icon PDF LinkTable of Contents
Conference Article|
August 01 2002
Cytochrome c maturation: a complex pathway for a simple task?
L. Thöny-Meyer
L. Thöny-Meyer
1
1Institut für Mikrobiologie, Departement Biologie, ETH Zentrum, CH-8092 Zürich, Switzerland
1E-mail lthoeny@micro.biol.ethz.ch
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
March 11 2002
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© 2002 Biochemical Society
2002
Biochem Soc Trans (2002) 30 (4): 633–638.
Article history
Received:
March 11 2002
Citation
L. Thöny-Meyer; Cytochrome c maturation: a complex pathway for a simple task?. Biochem Soc Trans 1 August 2002; 30 (4): 633–638. doi: https://doi.org/10.1042/bst0300633
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Captcha Validation Error. Please try again.