Amino acid sequence, binding properties and evolutionary relationships of the basic liver fatty-acid-binding protein from the catfish Rhamdia sapo

Abstract

The complete amino acid sequence of a basic liver fatty acid-binding protein (L-FABP) from catfish (Rhamdia sapo) was determined. Alignment of sequences shows that it has more similarity to chicken basic L-FABP than to mammalian L-FABP. The phylogenetic analysis suggests that basic L-FABP from catfish, chicken and iguana diverged from the mammalian protein before the fish-tetrapod divergence thus implying that the two types are encoded by different genes. Supporting this conclusion, a 14-kDa protein, structurally closely related to mammalian L-FABP, was isolated from catfish intestine, indicating the presence of the two genes in the same species. The catfish basic L-FABP binds only one fatty acid/molecule, while mammalian L-FABP bind two. The former has more affinity for trans-parinaric acid than for cis-parinaric acid, in constrat to the latter proteins.