The thioreduction component CcmG confers efficiency and the heme ligation component CcmH ensures stereo-specificity during cytochrome c maturation
- Pennsylvania State Univ., University Park, PA (United States). Dept. of Biology
- Univ. of Kutztown, Kutztown, PA (United States). Dept. of Physical Sciences
- Univ. of Texas at El Paso, TX (United States). Dept of Biological Sciences
In many Gram-negative bacteria, including Rhodobacter capsulatus, cytochrome c maturation (Ccm) is carried out by a membrane-integral machinery composed of nine proteins (CcmA to I). During this process, the periplasmic thiol-disulfide oxidoreductase DsbA is thought to catalyze the formation of a disulfide bond between the Cys residues at the apocytochrome c heme binding site (CXXCH). Subsequently, a Ccm-specific thioreductive pathway involving CcmG and CcmH reduces this disulfide bond to allow covalent heme ligation. Currently, the sequence of thioredox reactions occurring between these components and apocytochrome c, and the identity of their active Cys residues are unknown. In this work, we first investigated protein-protein interactions among the apocytochrome c, CcmG, and the heme ligation components CcmF, CcmH, and CcmI. We found that they all interact with each other, forming a CcmFGHI-apocytochrome c complex. Using purified wild-type CcmG, CcmH, and apocytochrome c, as well as their respective Cys mutant variants we determined the rates of thiol-disulfide exchange reactions between selected pairs of Cys residues from these proteins. We established that CcmG can efficiently reduce the disulfide bond of apocytochrome c and also resolve a mixed disulfide bond formed between apocytochrome c and CcmH. We further show that C45 of CcmH and C34 of apocytochrome c are most likely to form this mixed disulfide bond, which is consistent with the stereo-specificity of the heme-apocytochrome c ligation reaction. We conclude that CcmG confers efficiency, and CcmH ensures stereo-specificity during Ccm, and present a comprehensive model for thioreduction reactions that lead to heme-apocytochrome c ligation.
- Research Organization:
- Univ. of Pennsylvania, Philadelphia, PA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Grant/Contract Number:
- FG02-91ER20052
- OSTI ID:
- 1535361
- Journal Information:
- Journal of Biological Chemistry, Vol. 292, Issue 32; ISSN 0021-9258
- Publisher:
- American Society for Biochemistry and Molecular BiologyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
The CcmC–CcmE interaction during cytochrome c maturation by System I is driven by protein–protein and not protein–heme contacts
|
journal | September 2018 |
Oxidative protein folding: state‐of‐the‐art and current avenues of research in plants
|
journal | September 2018 |
Absence of Thiol-Disulfide Oxidoreductase DsbA Impairs cbb3-Type Cytochrome c Oxidase Biogenesis in Rhodobacter capsulatus
|
journal | December 2017 |
Similar Records
Maturation of Plastid c-type Cytochromes
Two disulfide-reducing pathways are required for the maturation of plastid c -type cytochromes in Chlamydomonas reinhardtii