AJP - Cell Physiology, Vol 259, Issue 4 C619-C630, Copyright © 1990 by American Physiological Society
Stability of Na(+)-K(+)-ATPase alpha-subunit isoforms in evolution
K. Takeyasu, V. Lemas and D. M. Fambrough
Department of Physiology, University of Virginia School of Medicine, Charlottesville 22908.
Encoding DNA for alpha 2- and alpha 3-isoforms of the alpha-subunit of the
chicken Na(+)-K(+)-ATPase have been cloned, and their nucleotide sequences
and deduced amino acid sequences are reported. Comparisons between these
data and comparable data for the rat alpha-subunit isoforms make possible
an assessment of alpha-subunit isoform diversity among vertebrates. There
is approximately twice as much amino acid sequence difference between
alpha-isoforms within a single species as there is difference between
corresponding alpha-isoforms of bird and mammal. These data are consistent
with triplication of the alpha-subunit gene and evolution of substantially
different alpha-subunit isoforms before the separation of avian and
mammalian lineages over 200 million years ago and then retention of the
majority of these structural differences through subsequent evolution. The
implications of this conversation of isoform-specific structural features
are discussed in terms of transport functions and bioregulation of the
Na(+)-K(+)-ATPase.
