A monoclonal antibody to kidney endopeptidase-24.11. Its application in immunoadsorbent purification of the enzyme and immunofluorescent microscopy of kidney and intestine

Abstract

Hybridoma methodology was used to produce a monoclonal antibody, GK 7C2, that binds specifically to microvillar endopeptidase-24,11 (EC 3,4,24,11). The antibody (an IgG) was generated by fusion of mouse plasmacytoma cells with splenocytes from a Balb/c mouse immunized with pig kidney microvillar membranes. The identity of the antigen recognized by GK 7C2 was established by immunoprecipitation form detergent-solubilized pig kidney microvilli. The protein had an apparent MW or 90,000 and contained endopeptidase activity sensitive to phosphoramidon. Identity was confirmed by immunoadsorbent purification of endopeptidase-24.11 by a column to which GK 7C2 had been attached. The endopeptidase, purified in a yield of 40%, was electrophoretically homogeneous and of specific activity comparable with that purified by other means. Fluorescence microscopy established that GK 7C2 bound specifically to luminal membranes of kidney tubules and intestinal mucosa. Endopeptidase-24.11 is located in brush-border membranes of both cell types.