Cytochrome c Oxidase Assembly in Primates is Sensitive to Small Evolutionary Variations in Amino Acid Sequence

Abstract

Respiring mitochondria require many interactions between nuclear and mitochondrial genomes. Although mitochondrial DNA (mtDNA) from the gorilla and the chimpanzee are able to restore oxidative phosphorylation in a human cell, mtDNAs from more distant primate species are functionally incompatible with human nuclear genes. Using microcell-mediated chromosome and mitochondria transfer, we introduced and maintained a functional orangutan mtDNA in a human nuclear background. However, partial oxidative phosphorylation function was restored only in the presence of most orangutan chromosomes, suggesting that human oxidative phosphorylation-related nuclear-coded genes are not able to replace many orangutan ones. The respiratory capacity of these hybrids was decreased by 65%-80%, and cytochrome c oxidase (COX) activity was decreased by 85%-95%. The function of other respiratory complexes was not significantly altered. The translation of mtDNA-coded COX subunits was normal, but their steady-state levels were approximately 10% of normal ones. Nuclear-coded COX subunits were loosely associated with mitochondrial membranes, a characteristic of COX assembly-defective mutants. Our results suggest that many human nuclear-coded genes not only cannot replace the orangutan counterparts, but also exert a specific interference at the level of COX assembly. This cellular model underscores the precision of COX assembly in mammals and sheds light on the nature of nuclear-mtDNA coevolutionary constraints.

The role of mitochondrial respiration in physiological and evolutionary adaptation

“…In experiments with rodent and primate xenomitochondrial cybrids, protein translation was not affected but steadystate levels of subunits decreased, indicating that reduced respiratory activity was due to problems in enzyme complex assembly. (87,88) Complementing these experimental studies, sequence analysis shows that amino acids in contact with other subunits and non-contact residues differ in patterns of substitution, consistent with the hypothesis of cytonuclear coevolution. In mammalian COX subunits, residues on nuclear-encoded subunits evolve more slowly when in close proximity to mitochondrially encoded subunits; in contrast, mitochondrially encoded residues in contact with other subunits evolve more rapidly than non-contacting amino acids, which may allow optimizing interactions with residues on nuclear-encoded subunits.…”

Role‐reversal of gender‐associated mitochondrial DNA affects mitochondrial function in Mytilus edulis (Bivalvia: Mytilidae)

“…One of these four inferred (Table 2). Because cytochrome c oxidase complex assembly has been shown to be sensitive to small differences in amino acid sequences not necessarily involved in the catalytic function (i.e., substitutions that could modify the interaction between nuclear and mitochondrial subunits at positions of structural importance to enzyme function), all these changes could have functional consequences (e.g., Barrientos et al, 2000).…”

Mitonuclear coevolution as the genesis of speciation and the mitochondrial DNA barcode gap

“…In cell cultures in which nuclear DNA from one species is forced to cofunction with mt DNA from a closely related species in cybrid cells, the efficiency of OXPHOS is invariably significantly compromised (Kenyon and Moraes 1997; Barrientos et al. 2000; McKenzie et al. 2003).…”