Primary structure of a 15‐kDa protein from rat intestinal epithelium: Sequence similarity to fatty‐acid‐binding proteins

Abstract

An abundant and novel cytosolic protein was purified from the rat intestinal epithelium by gel filtration, ionexchange and hydroxylapatite chromatography. The protein was eluted into two different positions (fractions 1 and 2) on DEAE‐cellulose chromatography. We have completed the primary structure of the protein of fraction 1 by Edman degradation. The protein (144 565 Da) contains 127 amino acid residues and has an acetylated alanine at its NH 2‐terminus. Comparison of the primary structure of the protein with porcine gastrotropin [Walz, A. D., Wider, M. D., Snow, J. W., Dass, C. & Desiderio, D. M. (1988) J. Biol. Chem. 263, 14189–14195] and rat hepatic fatty‐acid‐binding protein revealed that identical residues within these proteins are found in 90 and 54 out of a total of 127 positions, respectively. Bioactivity studies demonstrated that neither the protein nor liver and intestinal fatty‐acid‐binding proteins influence gastric acid secretory activity in rats with gastric fistulas compared to pentagastrin. The protein showed very low affinity for palmitic‐acid‐binding in vitro assay system and only trace amounts of endogenous fatty acids were detected from the protein. The protein, rat intestinal 15‐kDa protein is considered to be a new member of the fatty‐acid‐binding protein family based on its structural features.