Purification and Immuno- histochemical Localization of a 17-kD Porcine Renal Puromycin Aminonucleoside Binding Protein

We have purified a 17-kD puromycin aminonucleoside (PAN) binding protein from porcine kidney and identified it as the reported 17-kD protein kinase C inhibitor on the basis of its partial amino acid sequence. Of 54 determined amino acid sequences of the 17-kD porcine renal protein, 51 residues were identical to those of the 17-kD bovine brain protein kinase C inhibitor. However, our purified protein did not carry the inhibitory activity on protein kinase C. Immunohistochemical studies showed a unique intrarenal distribution of the 17-kD PAN-binding protein at the apical side of epithelial cells of Henle’s loops in the inner medulla and of distal convoluted tubules. Immunoblot analysis revealed that the 17-kD PAN-binding protein was extractable by an isotonic buffer without sodium deoxycholate extraction. These results suggest that this protein binds loosely to the apical membranes of epithelial cells of Henle’s loops and distal tubules and has specific functions related to tubular functions of these nephron segments at the apical side. Whether this protein is a real inhibitor of protein kinase C or not remains to be investigated.