title: Characterization and primary structure of a fatty acid-binding protein and its isoforms from the liver of the Amphibia, Rana catesbeiana.
abstract: Fatty acid-binding protein (FABP) was purified from the liver of the Amphibia, Rana catesbeiana, by gel filtration and ion-exchange chromatography. The complete primary structure of the frog liver FABP was determined by protein analysis. Two isoforms, I and II, were separated by reversed phase HPLC, and found to differ by 10 atomic mass units as measured by ion-spray ionization mass spectrometry. A detailed analysis of enzymatic peptides revealed a single Pro (isoform I)/Ser (isoform II) replacement at position 16. It seems remarkable that a rather neutral point mutation results in the nearly complete separation of the two isoforms by reversed phase chromatography. Homology modeling suggests the location of this site on the first helix of the helix-turn-helix domain and the presence of a single thiol group of cysteine-91 at the inside of the ligand-binding cavity. Binding studies using a natural fluorescent fatty acid, cis-parinaric acid, showed a lower Kd value for the serine form and large enhancement of fluorescence intensity upon glutathione-thiolation at cysteine-91. Examination of phylogenetic relationships identified the frog liver protein as a mammalian liver type FABP, and suggested a change in the vertebrate liver FABP gene expression at the bony fish/cartilagenous fish boundary.
authors.affiliation: Department of Biology, Faculty of Science, Niigata University, Niigata, 950-2181, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Baba
authors.forename: T K
authors.initials: TK
authors.lastname: Abe
authors.forename: S
authors.initials: S
authors.lastname: Tsunasawa
authors.forename: S
authors.initials: S
authors.lastname: Odani
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000737:chemistry; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D008099:Liver / Q000737:chemistry*; D008297:Male; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D018996:Myelin P2 Protein / Q000737:chemistry* / Q000302:isolation & purification / Q000502:physiology*; D009363:Neoplasm Proteins; D010802:Phylogeny; D011487:Protein Conformation; D020033:Protein Isoforms; D011892:Rana catesbeiana; D013438:Sulfhydryl Compounds
chemical_list: D002352:Carrier Proteins; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D013438:Sulfhydryl Compounds; D003545:Cysteine