NA-ATPASE ISOZYMES IN THE BOVINE BRAI N GREY-MATTER AND STEM(,K+)

An active preparations of Na+, K+-ATPase containing three types of cat alytic isoforms were isolated from the bovine brain to study the struc ture and function of the sodium pump. It was found, that Na+, K+-ATPas e from the brain grey matter was characterized by the biphasic kinetic s with respect to ouabain inhibition and consisted of a set of isozyme s with subunit composition of alpha 1 beta 1, alpha 2 beta m and alpha 3 beta m (where m = 1 and/or 2), moreover, the alpha 1 beta 1 form do minated clearly. For the first time, different glycosylation of the be ta 1-subunit of the alpha 1 beta 1-type isozymes from the kidney and b rain was shown. Na+, K+-ATPase from the brain stem and axolemma consis ted mainly of a mixture of alpha 2 beta 1 and alpha 3 beta 1 isozymes having identical ouabain inhibition constants. In epithelial and arter ial smooth muscle cells, in which the plasma membrane is divided into functionally and biochemically distinct domains, the polarized distrib ution of Na+ . K+-ATPase is maintained through interactions with the m embrane cytoskeleton proteins ankyrin and spectrin (Nelson & Hammerton , 1989; Lee et al., 1996). We were the first to show the presence of t he cytoskeleton protein tubulin (beta 5- isoform) and glyceraldehyde-3 -phosphate dehydrogenase in a high-molecular-weight complex with Na+, K+-ATPase in brain stem neuron cells containing alpha 2 beta 1 and alp ha 3 beta 1 isozymes. Consequently the influence of not only subunit c omposition, but also of glycan and cytoskeleton structures and other p lasma membrane-associated proteins on the functional properties of Na, K+-ATPase isozymes is evident.