Structural and Biochemical Characterization of the Lungfish (Lepidosiren paradoxa) Liver Basic Fatty Acid Binding Protein

Only one fatty acid-binding protein (FABP) from the liver of the lungfish (Lepidosiren paradoxa) was isolated and characterized. The sequence comparison of lungfish FABP with that of the known members of the liver FABP (L-FABP) and liver basic FABP (Lb-FABP) subfamilies indicates that it is more closely related to chicken, iguana, frog, axolotl, catfish, and shark Lb-FABPs than to mammalian and axolotl L-FABPs. Lungfish liver expression of this single Lb-FABP contrasts with the other fish studied so far which coexpress an Lb-FABP with heart-adipocyte and/or intestinal FABP types. The lungfish liver FABP expression pattern resembles that of tetrapods, which only expresses liver type FABPs. Lungfish Lb-FABP is one of the two FABPs reported to have a disulfide bridge. The molecular modeling of lungfish Lb-FABP predicts that nine of the conserved residues of Lb-FABPs are oriented toward the binding cavity, thus suggesting they are related to the protein binding characteristics.