TY - JOUR
T1 - Adaptive evolution of cytochrome c oxidase
T2 - Infrastructure for a carnivorous plant radiation
AU - Jobson, Richard W.
AU - Nielsen, Rasmus
AU - Laakkonen, Liisa
AU - Wikström, Mårten
AU - Albert, Victor A.
PY - 2004/12/28
Y1 - 2004/12/28
N2 - 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 ≈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.
AB - 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 ≈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.
KW - Cellular energetics
KW - Developmental regulation
KW - Molecular adaptation
KW - Positive selection
KW - Protein structure
UR - http://www.scopus.com/inward/record.url?scp=11144246408&partnerID=8YFLogxK
U2 - 10.1073/pnas.0408092101
DO - 10.1073/pnas.0408092101
M3 - Journal article
C2 - 15596720
AN - SCOPUS:11144246408
SN - 0027-8424
VL - 101
SP - 18064
EP - 18068
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 52
ER -