Adaptive evolution of cytochrome c oxidase: Infrastructure for a carnivorous plant radiation

Proc Natl Acad Sci U S A. 2004 Dec 28;101(52):18064-8. doi: 10.1073/pnas.0408092101. Epub 2004 Dec 13.

Abstract

Much recent attention in the study of adaptation of organismal form has centered on developmental regulation. As such, the highly conserved respiratory machinery of eukaryotic cells might seem an unlikely target for selection supporting novel morphologies. We demonstrate that a dramatic molecular evolutionary rate increase in subunit I of cytochrome c oxidase (COX) from an active-trapping lineage of carnivorous plants is caused by positive Darwinian selection. Bladderworts (Utricularia) trap plankton when water-immersed, negatively pressured suction bladders are triggered. The resetting of traps involves active ion transport, requiring considerable energy expenditure. As judged from the quaternary structure of bovine COX, the most profound adaptive substitutions are two contiguous cysteines absent in approximately 99.9% of databased COX I sequences from Eukaryota, Archaea, and Bacteria. This motif lies directly at the docking point of COX I helix 3 and cytochrome c, and modeling of bovine COX I suggests the possibility of an unprecedented helix-terminating disulfide bridge that could alter COX/cytochrome c dissociation kinetics. Thus, the key adaptation in Utricularia likely lies in molecular energetic changes that buttressed the mechanisms responsible for the bladderworts' radical morphological evolution. Along with evidence for COX evolution underlying expansion of the anthropoid neocortex, our findings underscore that important morphological and physiological innovations must often be accompanied by specific adaptations in proteins with basic cellular functions.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / chemistry
  • Amino Acid Motifs
  • Animals
  • Biological Evolution
  • Cattle
  • Conserved Sequence
  • Cysteine / chemistry
  • Electron Transport Complex IV / genetics*
  • Evolution, Molecular*
  • Exons
  • Genes, Plant
  • Ions
  • Kinetics
  • Magnoliopsida / genetics*
  • Models, Molecular
  • Molecular Sequence Data
  • Phylogeny
  • Plants / enzymology
  • Polymerase Chain Reaction
  • Protein Conformation
  • Protein Structure, Quaternary
  • Sequence Analysis, DNA

Substances

  • Ions
  • Adenosine Triphosphate
  • Electron Transport Complex IV
  • Cysteine

Associated data

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