~ Pergamon 0305-0491(94)00095-6 Comp. Biochem. Physiol. Vol. 109B,No. 2/3, pp. 199-208, 1994 Copyright © 1994Elsevier ScienceLtd Printed in Great Britain.All rights reserved 0305-0491/94 $7.00+ 0.00 MINI REVIEW Fatty acid binding protein in locust and mammalian muscle. Comparison of structure, function and regulation Norbert H. Haunerland Department of Biological Sciences, Simon Fraser University, Burnaby, B.C., Canada V5A lS6 The flight muscle of adult desert locusts, Schistocerca gregaria, contains a fatty acid binding protein (FABP) that is homologous to mammalian M-FABP (cardiac FABP). In spite of the evolutionary distance between invertebrates and vertebrates, locust muscle FABP is similar to cardiac FABP in its amino acid sequence, structure, and binding behavior. While cardiac FABP is present already in the prenatal period, locust FABP is an adult specific protein; its expression is directly linked to metamorphosis. A correlation seems to exist between fatty acid oxidative capacity and FABP content in both locust and mammals. To accomplish the higher metabolic rate encountered during migratory flight, locust 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. Similarities and differences between vertebrate and invertebrate M-FABP are discussed in light of the proposed functions of muscle FABP as fatty acid transporter and cytoprotectant. Key words: FABP; Fatty acid transport; Fatty acid oxidation; Metabolic rate; Metabolic adaptation; Exercise; Flight. Comp. Biochem. Physiol. 109B, 199-208, 1994. Introduction Since their discovery by Ockner et al. (1972), fatty acid binding proteins (FABPs) have been studied intensely in many differ- ent tissues and organisms. Many details of Correspondence to: N. H. Haunerland, Dept. of Biological Sciences, Simon Fraser University, Burnaby, B.C. V5A 1S6 Canada. Tel. 602 291- 3734; Fax 602 291-3496; Internet: norbert_hauner- land@sfu.ca Abbreviations--AKH, adipokinetic hormone; FABP, fatty acid binding protein; A-FABP, adipocyte FABP;, L-FABP, liver FABP; M-FABP, muscle FABP; I-FABP, intestinal FABP; LDLp, low density lipophorin. Received 22 January 1994; accepted 20 May 1994. their structure, cell and tissue specificity and binding properties are now well understood. While all of these ubiquitous intracellular proteins are structurally related, it is now apparent that different binding proteins are expressed in different tissues. At least four distinct FABPs have been identified: intestinal (I-FABP), hepatic (L-FABP), muscle (M-FABP) and adipocyte FABP (A-FABP). These proteins belong to a superfamily of lipid binding proteins that also include myelin P2 protein, cellular retinol binding protein and cellular retinoic acid binding protein (Matarese et al., 1989). All these proteins 199