One-step purification of rat heart-type fatty acid-binding protein expressed in Escherichia coli.

Heart-type fatty acid-binding protein (H-FABP) is a member of a family of 14-15 kDa lipid binding proteins which are believed to enhance intracellular transport of lipids by facilitating their cytoplasmic diffusion. To obtain sufficient amounts of protein for in vitro studies, we expressed rat H-FABP in Escherichia coli and compared its biochemical properties with the protein isolated from rat heart. An effective method was developed to purify recombinant rat H-FABP from cell lysates in a single step using anion-exchange chromatography. This method also proved to be applicable for purifying heterologously expressed human H-FABP. Recombinant rat H-FABP, which made up approximately 25% of the soluble proteins in E. coli, was obtained in a yield of 30-40 mg/l culture. Characterization showed that recombinant rat H-FABP was indistinguishable from the protein isolated from rat heart regarding molecular mass and oleic acid binding. Some heterogeneity upon isoelectric focusing was observed, presumably due to differences in N-terminal processing of the proteins. In conclusion, a method is presented for efficient high-yield production of recombinant rat H-FABP.