Protein Machineries Involved in the Attachment of Heme to Cytochrome c: Protein Structures and Molecular Mechanisms

Figure 2

Schematic representation of the protein components of System I. Proteins involved in the heme translocation and delivery pathway are shown in light brown; proteins involved in the apoCyt thioreduction pathway are shown in green; proteins involved in apoCyt chaperoning and heme attachment processes are shown in light purple. Cyt c (the 3D structure is that of the Cyt c551 from P. aeruginosa), Protein Data Bank accession number 2EXV [20] and apoCyt (represented as a cartoon) are shown in blue. The translocation process of heme (shown in red) is unknown. The 3D structures of the soluble periplasmic domains of Ec-CcmE, Pa-CcmG and Pa-CcmH are shown (Protein Data Bank accession numbers are 1LIZ [21], 3KH7 [22], and 2HL7 [23], resp.). Organisms employing System I: - and -proteobacteria, some -proteobacteria (e.g., Nitrosomonas) and -proteobacteria (e.g., Desulfovibrio), and Deinococci and Archaea. Additionally, System I is observed in plant mitochondria and in the mitochondria of some protozoa (e.g., Tetrahymena).