Cancer Biol Med, 1998, 12(3):435-439

Na+,K+-ATPase isozymes in the bovine brain grey matter and brain stem

Active preparations of Na+,K+-ATPase containing three types of catalytic isoforms were isolated from the bovine brain to study the structure and function of the sodium pump. Na+,K+-ATPase from the brain grey matter was found to have a biphasic kinetics with respect to ouabain inhibition and to consist of a set of isozymes with subunit composition of α1β1, α2βm and α3βm (where m = 1 and/or 2). The α1β1 form clearly dominated. For the first time, glycosylation of the β1-subunit of the α1β1-type isozymes isolated from the kidney and brain was shown to be different. Na+,K+-ATPase from the brain stem and axolemma consisted mainly of a mixture of α2β1 and α3β1 isozymes having identical ouabain inhibition constants. In epithelial and arterial smooth muscle cells, where the plasma membrane is divided into functionally and biochemically distinct domains, the polarized distribution of Na+,K+-ATPase is maintained through interactions with the membrane cytoskeleton proteins ankyrin and spectrin. We were the first to show the presence of the cytoskeleton protein tubulin (β5-isoform) and glyceraldehyde-3-phosphate dehydrogenase in a high-molecular-weight complex with Na+,K+-ATPase in brain stem neuron cells containing α2β1 and α3β1 isozymes. Consequently, the influence of not only subunit composition, but also of glycan and cytoskeleton structures and other plasma membrane-associated proteins on the functional properties of Na+,K+-ATPase isozymes is evident.

IBCH: 5966
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