FATTY-ACID-BINDING PROTEIN IN LOCUST AND MAMMALIAN MUSCLE - COMPARISON OF STRUCTURE, FUNCTION AND REGULATION

The flight muscle of adult desert locusts, Schistocerca gregaria, cont ains a fatty acid binding protein (FABP) that is homologous to mammali an M-FABP (cardiac FABP). In spite of the evolutionary distance betwee n invertebrates and vertebrates, locust muscle FABP is similar to card iac FABP in its amino acid sequence, structure, and binding behavior. While cardiac FABP is present already in the prenatal period, locust F ABP is an adult specific protein; its expression is directly linked to metamorphosis. A correlation seems to exist between fatty acid oxidat ive capacity and FABP content in both locust and mammals. To accomplis h the higher metabolic rate encountered during migratory flight, locus t flight muscle cytosol contains more than three times as much FABP as that in mammalian heart. Increased fatty acid utilization by exercise or endurance training apparently induces FABP expression. Similaritie s and differences between vertebrate and invertebrate M-FABP are discu ssed in light of the proposed functions of muscle FABP as fatty acid t ransporter and cytoprotectant.