Isolation and partial characterization of an amphiphilic 56-kDa fatty acid binding protein from rat renal basolateral membrane.

We have identified a 56-kDa fatty acid binding protein in rat renal basolateral membrane and purified it by extraction in nonionic detergent (Triton X-100), followed by gel filtration, DEAE-cellulose chromatography, and affinity chromatography. The purified protein was homogeneous on polyacrylamide gel electrophoresis in the presence of Triton X-100 or SDS. It showed amphiphilic properties on gel filtration, polyacrylamide gel electrophoresis, and oleate-Sepharose 4B chromatography. Its molecular mass was estimated to be 56 kDa by SDS-polyacrylamide gel electrophoresis. The protein showed optimal binding activity at pH 7.5 and 37 degrees C. The apparent Kd for palmitic acid was 0.79 microM. It was immunologically clearly distinct from renal cytosolic fatty acid binding protein.