Isolation, characterization and binding properties of two rat liver fatty acid-binding protein isoforms.
Mammalian liver has only one fatty acid-binding protein (L-FABP) while the liver of non-mammalian vertebrates expresses a liver basic FABP (Lb-FABP) in addition to other members of the FABP family. We explore the possibility that L-FABP isoforms accomplish, in the liver of mammals, the metabolic functions corresponding to the different FABPs present in the liver of non-mammalian vertebrates. We have isolated isoforms I and II which have a different residue 105, Asn in the former and Asp in the latter. We made a conformational comparison of the apo-isoforms by intrinsic fluorescence emission and fourth-derivative spectroscopy, native-state proteolysis and unfolding curves. Ligand affinity was studied by measuring cis-parinaric acid displacement by different ligands. They have differences in their molecular conformation, including the environment of the binding site. Isoform II has probably a more open conformation than isoform I, thus allowing the binding of a greater variety of ligands. The affinity of isoform II for lysophospholipids, prostaglandins, retinoids, bilirubin and bile salts is greater than that of isoform I. These characteristics of rat L-FABP isoforms I and II suggest that they may accomplish different functions as happens with those of the different FABP types in non-mammalian species.
Di Pietro
S M
SM
Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, 1113, Buenos Aires, Argentina. santome@qb.ffyb.uba.ar
Santomé
J A
JA
D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002458:Cell Fractionation; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005231:Fatty Acids, Unsaturated; D005456:Fluorescent Dyes; D007525:Isoelectric Focusing; D008099:Liver / Q000378:metabolism*; D008297:Male; D018996:Myelin P2 Protein / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D017510:Protein Folding; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014357:Trypsin
D002352:Carrier Proteins; C493320:Fabp1 protein, mouse; C493321:Fabp1 protein, rat; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005231:Fatty Acids, Unsaturated; D005456:Fluorescent Dyes; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D010450:Endopeptidases; D014357:Trypsin; C013641:parinaric acid