Cytochrome c biogenesis System I: An intricate process catalyzed by a maturase supercomplex?

• Published in: Biochimica et biophysica acta 2014-07, Vol.1837 (7), p.989-998
• Main Authors: Verissimo, Andreia F., Daldal, Fevzi
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Apocytochrome; Archaeal Proteins - chemistry; Archaeal Proteins - metabolism; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Chaperone; Cytochrome c maturation; Cytochromes c - chemistry; Cytochromes c - metabolism; Electron Transport Chain Complex Proteins - chemistry; Electron Transport Chain Complex Proteins - metabolism; Humans; Membrane supercomplex; Molecular Sequence Data; Photosynthesis and respiration; Protein Binding; Protein–protein interactions; Rhodobacter capsulatus
• ISSN: 0005-2728; 0006-3002; 1879-2650
• DOI: 10.1016/j.bbabio.2014.03.003

Cytochromes c are ubiquitous heme proteins that are found in most living organisms and are essential for various energy production pathways as well as other cellular processes. Their biosynthesis relies on a complex post-translational process, called cytochrome c biogenesis, responsible for the formation of stereo-specific thioether bonds between the vinyl groups of heme b (protoporphyrin IX-Fe) and the thiol groups of apocytochromes c heme-binding site (C1XXC2H) cysteine residues. In some organisms this process involves up to nine (CcmABCDEFGHI) membrane proteins working together to achieve heme ligation, designated the Cytochrome c maturation (Ccm)-System I. Here, we review recent findings related to the Ccm-System I found in bacteria, archaea and plant mitochondria, with an emphasis on protein interactions between the Ccm components and their substrates (apocytochrome c and heme). We discuss the possibility that the Ccm proteins may form a multi subunit supercomplex (dubbed “Ccm machine”), and based on the currently available data, we present an updated version of a mechanistic model for Ccm. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference. •Cytochrome c biogenesis is the covalent ligation of heme b to an apocyt c.•Ccm is an intricate post-translational protein modification process.•Ccm-System I involves nine membrane-bound proteins working together.•The Ccm proteins are proposed to form a large multi subunit supercomplex.•A mechanistic view of stereo-specific thioether bond formation is presented.