Recognition of sodium- and potassium-dependent adenosine triphosphatase in organs of the mouse by means of a monoclonal antibody.

The antigen detected by the rat anti-mouse monoclonal antibody (m Ab), anti-BSP-3, has been initially described as a brain cell-surface protein. Evidence is presented that this m Ab recognizes mouse (Na+ + K+)-ATPase (ATP phosphohydrolase, E.C.3.6.1.3). The antigen, purified from mouse brain by means of affinity chromatography, migrated in SDS-polyacrylamide gels in the form of two polypeptide chains of 100 000 and 48 000 molecular weight, which could be shown to react with subunit-specific polyclonal antisera against ATPase in immunoblotting experiments. Purified BSP-3 antigen was bound to the specific (Na+ + K+)-ATPase inhibitor ouabain. Finally, the anti-BSP-3 m Ab was capable of immunoprecipitating the ATPase activity of a microsomal fraction from mouse kidney. The m Ab was used to study the localization of (Na+ + K+)-ATPase in different organs of the mouse. It stained the basolateral plasma membranes of polarized cells in immunofluorescence experiments, while the entire cell surface of unpolarized cells was labeled. Interestingly, several cell types did not react with the m Ab, indicating a possible heterogeneity of ATPases. Such a m Ab could prove to be a useful tool for studying localization, structure and function of (Na+ + K+)-ATPase.