2 DISTINCT TYPES OF FATTY-ACID-BINDING PROTEIN ARE EXPRESSED IN HEARTVENTRICLE OF ANTARCTIC TELEOST FISHES

This report provides the first evidence for the existence of two disti nct types of fatty acid-binding protein (FABP) in cardiac tissue of ve rtebrates. Four species of Antarctic teleost fish (Chaenocephalus acer atus, Cryodraco antarcticus, Gobionotothen gibberifrons and Notothenia coruceps) exhibited two FABP mRNAs of 1.0 kb and 0.8 kb, which we hav e termed H-h-FABP and H-ad-FABP (isolated from Heart tissue, with simi larity to mammalian heart-type FABP or mammalian adipose-type FABP res pectively). These FABP types appear to be products of distinct genes: Both FABP transcripts were abundant in cardiac and aerobic pectoral mu scle. However, relative abundance of the two types varied distinctly a mong other tissues such as kidney, brain, spleen and white muscle. Nei ther FABP type was expressed in liver or intestine. The coding regions of H-h-FABP and H-ad-FABP cDNAs from the same species are only simila r to 60 % identical with one another. However, homologues of each FABP species, which exhibit > 98 % identity to their respective types, wer e isolated from three other Antarctic teleosts. Phylogenetic analysis of aligned amino-acid sequences places H-h-FABP with other vertebrate heart-type FABPs, and H-ad with adipose/cutaneous FABPs. Expression of two distinct FABPs in cardiac tissue of Antarctic teleosts may be rel ated to their ability to both utilize fatty acid as the primary metabo lic fuel and to store lipid intracellularly.