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Title: The thioreduction component CcmG confers efficiency and the heme ligation component CcmH ensures stereo-specificity during cytochrome c maturation

Journal Article · · Journal of Biological Chemistry
 [1];  [1];  [1];  [1];  [1];  [2];  [3];  [1]
  1. Pennsylvania State Univ., University Park, PA (United States). Dept. of Biology
  2. Univ. of Kutztown, Kutztown, PA (United States). Dept. of Physical Sciences
  3. 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
Citation Metrics:
Cited by: 13 works
Citation information provided by
Web of Science

References (50)

Cytochrome c biogenesis: the Ccm system journal June 2010
Structure and mechanisms of the DsbB–DsbA disulfide bond generation machine journal April 2008
Structure and multistate function of the transmembrane electron transporter CcdA journal September 2015
Control of DegP-Dependent Degradation of c-Type Cytochromes by Heme and the Cytochrome c Maturation System in Escherichia coli journal July 2007
A Strategic Protein in Cytochrome c Maturation : THREE-DIMENSIONAL STRUCTURE OF CcmH AND BINDING TO APOCYTOCHROME c journal July 2007
Cleavage of Structural Proteins during the Assembly of the Head of Bacteriophage T4 journal August 1970
AtCCMH, an essential component of the c-type cytochrome maturation pathway in Arabidopsis mitochondria, interacts with apocytochrome c journal October 2005
Biochemical properties and catalytic domain structure of the CcmH protein from Escherichia coli journal December 2012
Helix swapping leads to dimerization of the N-terminal domain of the c -type cytochrome maturation protein CcmH from Escherichia coli journal July 2008
Cytochrome c biogenesis System I: An intricate process catalyzed by a maturase supercomplex? journal July 2014
Cytochrome c Biogenesis: Mechanisms for Covalent Modifications and Trafficking of Heme and for Heme-Iron Redox Control journal August 2009
The Heme Chaperone ApoCcmE Forms a Ternary Complex with CcmI and Apocytochrome c journal January 2013
Evolutionary domain fusion expanded the substrate specificity of the transmembrane electron transporter DsbD journal August 2002
The Cytochrome c Maturation Components CcmF, CcmH, and CcmI Form a Membrane-integral Multisubunit Heme Ligation Complex journal August 2008
The Escherichia coli CcmG protein fulfils a specific role in cytochrome c assembly journal February 2001
Recognition and binding of apocytochrome c to P. aeruginosa CcmI, a component of cytochrome c maturation machinery journal August 2013
Structural Basis and Kinetics of DsbD-Dependent Cytochrome c Maturation journal July 2005
Overexpression of ccl1−2 can bypass the need for the putative apocytochrome chaperone CycH during the biogenesis of c-type cytochromes: Suppressors of CycH-null mutants overexpress the ccl1-2 operon journal November 2002
Overproduction of CcmG and CcmFHRc Fully Suppresses the c-Type Cytochrome Biogenesis Defect of Rhodobacter capsulatus CcmI-Null Mutants journal June 2005
Formation and properties of mixed disulfides between thioredoxin reductase from Escherichia coli and thioredoxin: Evidence that cysteine-138 functions to initiate dithiol-disulfide interchange and to accept the reducing equivalent from reduced flavin journal June 1998
Cytochrome c assembly journal January 2013
A Cytochrome b 562 Variant with a c -Type Cytochrome C XX CH Heme-binding Motif as a Probe of the Escherichia coli Cytochrome c Maturation System journal October 2003
A thioreduction pathway tethered to the membrane for periplasmic cytochromes c biogenesis; in vitro and in vivo studies journal September 1997
Expression of prokaryotic and eukaryotic cytochromes c in Escherichia coli journal July 2000
Characterization of the Escherichia coli CcmH protein reveals new insights into the redox pathway required for cytochrome c maturation journal January 1999
Prediction of pKa and redox properties in the thioredoxin superfamily journal October 2004
Catalytic mechanism of the glutathione peroxidase-type tryparedoxin peroxidase of Trypanosoma brucei journal July 2007
Novel Rhodobacter capsulatus genes required for the biogenesis of various c-type cytochromes journal January 2000
During Cytochrome c Maturation CcmI Chaperones the Class I Apocytochromes until the Formation of Their b -Type Cytochrome Intermediates journal May 2015
Oxidation−Reduction Properties of Disulfide-Containing Proteins of the Rhodobacter capsulatus Cytochrome c Biogenesis System journal August 2000
Kinetics of the Intramolecular Disulfide Exchange Between the Periplasmic Domains of DsbD journal April 2007
Kinetic and thermodynamic studies on the disulfide-bond reducing potential of hydrogen sulfide journal April 2015
Cytochrome c :  Occurrence and Functions journal January 2006
Catalytic Mechanism of DsbA and Its Comparison with That of Protein Disulfide Isomerase journal March 1995
Two Snapshots of Electron Transport across the Membrane: INSIGHTS INTO THE STRUCTURE AND FUNCTION OF DsbD journal March 2009
The CcmFH complex is the system I holocytochrome c synthetase: engineering cytochrome c maturation independent of CcmABCDE : CcmFH is the system I holocytochrome journal January 2014
Structural and functional characterization of CcmG from Pseudomonas aeruginosa, a key component of the bacterial cytochrome c maturation apparatus journal May 2010
A Pivotal Heme-transfer Reaction Intermediate in Cytochrome c Biogenesis journal November 2011
The Sec translocon mediated protein transport in prokaryotes and eukaryotes journal March 2014
Structure and Function of DsbA, a Key Bacterial Oxidative Folding Catalyst journal May 2011
A Stable Mixed Disulfide between Thioredoxin Reductase and Its Substrate, Thioredoxin:  Preparation and Characterization journal January 1996
Reactivity of Thioredoxin as a Protein Thiol-Disulfide Oxidoreductase journal September 2011
Crystal structures of E. coli CcmG and its mutants reveal key roles of the N-terminal β-sheet and the fingerprint region journal October 2006
Compensatory thio-redox interactions between DsbA, CcdA and CcmG unveil the apocytochrome c holdase role of CcmG during cytochrome c maturation journal November 2008
The Dithiol:Disulfide Oxidoreductases DsbA and DsbB of Rhodobacter capsulatus Are Not Directly Involved in Cytochrome c Biogenesis, but Their Inactivation Restores the Cytochrome c Biogenesis Defect of CcdA-Null Mutants journal June 2003
Conferring specificity in redox pathways by enzymatic thiol/disulfide exchange reactions journal January 2016
Protein Disulfide Bond Formation in the Periplasm: Determination of the In Vivo Redox State of Cysteine Residues book November 2012
Structure of CcmG/DsbE at 1.14 Å Resolution journal July 2002
Mitochondrial thiol oxidase Erv1: both shuttle cysteine residues are required for its function with distinct roles journal May 2014
Membrane-Spanning and Periplasmic Segments of CcmI Have Distinct Functions during Cytochrome c Biogenesis in Rhodobacter capsulatus journal November 2006

Cited By (3)

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