Purification and liposomal reconstitution of the oligopeptide transport activity in rat renal cortex using...

The carrier protein(s) responsible for the transport of ceftibuten, a peptide-like dianionic cefem, in rat renal brush-border membrane were solubilized and purified by a ceftibuten-ligand specific affinity chromatography technique. The proteoliposomes reconstituted from the solubilized brush-border membrane proteins by dialysis had H+-sensitive uptake of ceftibuten and trans-stimulative effect by cephalexin. A specific uptake activity for ceftibuten was found in the 3.5 M-eluted fraction but not the flowthrough and the 0.5 M-eluted fraction of the affinity chromatography. Analyzing this active fraction by SDS/PAGE after reconstituting into liposomes gave two major proteins (approx. molecular masses of 130 and 107 kDa). The purification protocol presented in this study permitted an efficient isolation of the carrier proteins responsible for the transport of ceftibuten and other peptide-like compounds.