Maturation of the unusual single-cysteine (XXXCH) mitochondrial c-type cytochromes found in trypanosomatids must occur through a novel biogenesis pathway

• Published in: Biochemical journal Vol. 383; no. Pt. 3; pp. 537 - 542
• Main Authors: Allen, James W A, Ginger, Michael L, Ferguson, Stuart J
• Format: Journal Article
• Language: English
• Published: England Portland Press Ltd 01-11-2004
• Subjects: Amino Acid Motifs - genetics; Animals; Cysteine - genetics; Cytochrome c Group - biosynthesis; Cytochrome c Group - chemistry; Cytochrome c Group - genetics; Escherichia coli; Evolution, Molecular; Genetic Variation - genetics; Mitochondria - enzymology; Mitochondrial Proteins - biosynthesis; Mitochondrial Proteins - chemistry; Mitochondrial Proteins - genetics; Recombinant Proteins - biosynthesis; Recombinant Proteins - genetics; Trypanosoma brucei; Trypanosoma brucei brucei - enzymology; Trypanosomatidae
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj20040832

The c-type cytochromes are characterized by the covalent attachment of haem to the polypeptide via thioether bonds formed from haem vinyl groups and, normally, the thiols of two cysteines in a CXXCH motif. Intriguingly, the mitochondrial cytochromes c and c1 from two euglenids and the Trypanosomatidae contain only a single cysteine within the haem-binding motif (XXXCH). There are three known distinct pathways by which c-type cytochromes are matured post-translationally in different organisms. The absence of genes encoding any of these c-type cytochrome biogenesis machineries is established here by analysis of six trypanosomatid genomes, and correlates with the presence of single-cysteine cytochromes c and c1. In contrast, we have identified a comprehensive catalogue of proteins required for a typical mitochondrial oxidative phosphorylation apparatus. Neither spontaneous nor catalysed maturation of the single-cysteine Trypanosoma brucei cytochrome c occurred in Escherichia coli. However, a CXXCH variant was matured by the E. coli cytochrome c maturation machinery, confirming the proposed requirement of the latter for two cysteines in the haem-binding motif and indicating that T. brucei cytochrome c can accommodate a second cysteine in a CXXCH motif. The single-cysteine haem attachment conserved in cytochromes c and c1 of the trypanosomatids is suggested to be related to their cytochrome c maturation machinery, and the environment in the mitochondrial intermembrane space. Our genomic and biochemical studies provide very persuasive evidence that the trypanosomatid mitochondrial cytochromes c are matured by a novel biogenesis system.