Molecular Weight and Subunit Composition of the Sensitive to GABA-Ergic Ligands Cl^-/HCO₃^--Stimulated Mg²⁺-ATPase from Plasma Membrane of Rat Brain

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S. A. Menzikov^* and O. V. Menzikova

Institute of General Pathology and Pathophysiology, Russian Academy of Medical Sciences, ul. Baltiiskaya 8, 125315 Moscow, Russia; fax: (7-095) 151-1756; E-mail: menzikov@lansp.ru

^* To whom correspondence should be addressed.

Received December 6, 2004; Revision received December 22, 2004

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The molecular weight and subunit composition of Cl^-,HCO₃^-- and picrotoxin-stimulated Mg²⁺-ATPase from rat brain plasma membrane solubilized in sodium deoxycholate were studied by gel filtration chromatography. The enzyme activity eluted from a Sephacryl S-300 column in a single peak associated with a protein of molecular weight ~300 kD and a Stokes radius of 5.4 nm. The enzyme-enriched fraction, concentrated and denatured by SDS, migrated through a Sephacryl S-200 column as three peaks with molecular weights of approximately 57, 53, and 45 kD. SDS-PAGE also showed three major protein bands with molecular weights of about 57, 53, and 48 kD. The molecular weight and subunit composition of the Cl^- and HCO₃^--stimulated Mg²⁺-ATPase from neuronal membrane of rat brain are similar with the molecular properties of GABA_A-benzodiazepine receptor complex from mammalian brain but are different from those of P-type transport ATPases.

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KEY WORDS: rat, brain, plasma membranes, Cl^-,HCO₃^--ATPase, gamma-amino-n-butyric acid (GABA), picrotoxin, gel chromatography, molecular weight, subunit composition

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