Molecular Evolution of Cytochrome c Oxidase Underlies High-Altitude Adaptation in the Bar-Headed Goose

Graham R. Scott, Patricia M. Schulte, Stuart Egginton, Angela L. M. Scott, Jeffrey G. Richards, William K. Milsom

Research output: Contribution to journalArticlepeer-review

174 Citations (Scopus)

Abstract

Bar-headed geese (Anser indicus) fly at up to 9,000 m elevation during their migration over the Himalayas, sustaining high metabolic rates in the severe hypoxia at these altitudes. We investigated the evolution of cardiac energy metabolism and O-2 transport in this species to better understand the molecular and physiological mechanisms of high-altitude adaptation. Compared with low-altitude geese (pink-footed geese and barnacle geese), bar-headed geese had larger lungs and higher capillary densities in the left ventricle of the heart, both of which should improve O-2 diffusion during hypoxia. Although myoglobin abundance and the activities of many metabolic enzymes (carnitine palmitoyltransferase, citrate synthase, 3-hydroxyacyl-coA dehydrogenase, lactate dehydrogenase, and pyruvate kinase) showed only minor variation between species, bar-headed geese had a striking alteration in the kinetics of cytochrome c oxidase (COX), the heteromeric enzyme that catalyzes O-2 reduction in oxidative phosphorylation. This was reflected by a lower maximum catalytic activity and a higher affinity for reduced cytochrome c. There were small differences between species in messenger RNA and protein expression of COX subunits 3 and 4, but these were inconsistent with the divergence in enzyme kinetics. However, the COX3 gene of bar-headed geese contained a nonsynonymous substitution at a site that is otherwise conserved across vertebrates and resulted in a major functional change of amino acid class (Trp-116 -> Arg). This mutation was predicted by structural modeling to alter the interaction between COX3 and COX1. Adaptations in mitochondrial enzyme kinetics and O-2 transport capacity may therefore contribute to the exceptional ability of bar-headed geese to fly high.

Original languageEnglish
Pages (from-to)351-363
Number of pages13
JournalMolecular Biology and Evolution
Volume28
Issue number1
Early online date4 Aug 2010
DOIs
Publication statusPublished - Jan 2011

Keywords

  • exercise performance
  • phylogenetically independent contrasts
  • protein homology modeling
  • birds
  • avian
  • GEESE ANSER-INDICUS
  • HEMOGLOBIN GENES
  • GUINEA-PIGS
  • MUSCLE
  • MECHANISM
  • SUBUNIT
  • RESPIRATION
  • GRADIENT
  • HYPOXIA
  • FLIGHT

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