Expression in Escherichia coli and characterization of the fatty-acid-binding protein from human muscle

The coding part of the cDNA encoding human muscle fatty-acid-binding protein (FABP) was ligated in the pET8c vector and expressed under the control of the lacUV5 promoter. After induction with isopropyl beta-D-thiogalactopyranoside, almost 12% of the cytoplasmic proteins consisted of FABP. The protein could be isolated after sonication of the bacterial pellet followed by (NH4)2SO4 precipitations, anion-exchange chromatography and gel filtration. The muscle FABP produced in Escherichia coli has an isoelectric point of 5.3 and is recognized by anti-(human muscle FABP) antiserum after Western blotting. The purified FABP has a preference for binding to palmitic acid and C18-C22 (poly)unsaturated fatty acids, and no affinity to palmitoyl-CoA or other hydrophobic ligands tested. The dissociation constant for oleic acid is 0.58 microM, with a binding stoichiometry of 0.72 mol of fatty acid/mol of protein. The physicochemical and binding characteristics of the protein were in complete agreement with those of FABP isolated from human skeletal muscle.