Molecular evolution of the multigene family of intracellular lipid-binding proteins.

The intracellular lipid-binding proteins are a group of homologous proteins which bind and facilitate the transport of fatty acids, bile acids and retinoids. The evolutionary relationship of 51 family members from vertebrates and invertebrates was analyzed. The inferred phylogeny implies the occurrence of at least 14 gene duplications and contains five regions where the branching order is statistically non-significant--this uncertainty explaining most inconsistencies between previous phylogenetic analyses. The phylogeny also suggests that the intestinal fatty acid-binding protein and the liver fatty acid-binding protein/ileal lipid-binding protein subfamilies diverged from the other subfamilies before the vertebrate-invertebrate split. Finally, results presented herein indicate that the putative fatty acid-binding domain of NMDA receptor 1 is unlikely to be a member of this family.