Insights into binding of fatty acids by fatty acid binding proteins.
Members of the phylogenetically related intracellular lipid binding protein (iLBP) are characterized by a highly conserved tertiary structure, but reveal distinct binding preferences with regard to ligand structure and conformation, when binding is assessed by the Lipidex method (removal of unbound ligand by hydrophobic polymer) or by isothermal titration calorimetry, a true equilibrium method. Subfamily proteins bind retinoids, subfamily II proteins bind bulky ligands, examples are intestinal bile acid binding protein (I-BABP) and liver fatty acid binding protein (L-FABP) which binds 2 ligand molecules, preferably monounsaturated and n-3 fatty acids. Subfamily III intestinal fatty acid binding protein (I-FABP) binds fatty acid in a bent conformation. The fatty acid bound by subfamily IV FABPs has a U-shaped conformation; here heart (H-) FABP preferably binds n-6, brain (B-) FABP n-3 fatty acids. The ADIFAB-method is a fluorescent test for fatty acid in equilibrium with iLBP and reveals some correlation of binding affinity to fatty acid solubility in the aqueous phase; these data are often at variance with those obtained by the other methods. Thus, in this review published binding data are critically discussed, taking into account on the one hand binding increments calculated for fatty acid double bonds on the basis of the 'solubility' hypothesis, on the other hand the interpretation of calorimetric data on the basis of crystallographic and solution structures of iLBPs.
Hanhoff
Thorsten
T
Department of Biochemistry, University of Münster, Münster, Germany.
Lücke
Christian
C
Spener
Friedrich
F
D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D000074026:Fatty Acid Binding Protein 3; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D009363:Neoplasm Proteins; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013816:Thermodynamics; D025521:Tumor Suppressor Proteins
D002352:Carrier Proteins; C493319:FABP1 protein, human; C493408:FABP3 protein, human; C107608:FABP7 protein, human; C493320:Fabp1 protein, mouse; D000074026:Fatty Acid Binding Protein 3; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D008024:Ligands; D009363:Neoplasm Proteins; D025521:Tumor Suppressor Proteins