title: Solution structure of human intestinal fatty acid binding protein: implications for ligand entry and exit.
abstract: The human intestinal fatty acid binding protein (I-FABP) is a small (131 amino acids) protein which binds dietary long-chain fatty acids in the cytosol of enterocytes. Recently, an alanine to threonine substitution at position 54 in I-FABP has been identified which affects fatty acid binding and transport, and is associated with the development of insulin resistance in several populations including Mexican-Americans and Pima Indians. To investigate the molecular basis of the binding properties of I-FABP, the 3D solution structure of the more common form of human I-FABP (Ala54) was studied by multidimensional NMR spectroscopy. Recombinant I-FABP was expressed from E. coli in the presence and absence of 15N-enriched media. The sequential assignments for non-delipidated I-FABP were completed by using 2D homonuclear spectra (COSY, TOCSY and NOESY) and 3D heteronuclear spectra (NOESY-HMQC and TOCSY-HMQC). The tertiary structure of human I-FABP was calculated by using the distance geometry program DIANA based on 2519 distance constraints obtained from the NMR data. Subsequent energy minimization was carried out by using the program SYBYL in the presence of distance constraints. The conformation of human I-FABP consists of 10 antiparallel beta-strands which form two nearly orthogonal beta-sheets of five strands each, and two short alpha-helices that connect the beta-strands A and B. The interior of the protein consists of a water-filled cavity between the two beta-sheets. The NMR solution structure of human I-FABP is similar to the crystal structure of rat I-FABP. The NMR results show significant conformational variability of certain backbone segments around the postulated portal region for the entry and exit of fatty acid ligand.
authors.affiliation: Department of Biophysics, Boston University School of Medicine, Boston, MA 02118, USA.
authors.forename: F
authors.initials: F
authors.lastname: Zhang
authors.forename: C
authors.initials: C
authors.lastname: Lücke
authors.forename: L J
authors.initials: LJ
authors.lastname: Baier
authors.forename: J C
authors.initials: JC
authors.lastname: Sacchettini
authors.forename: J A
authors.initials: JA
authors.lastname: Hamilton
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002151:Calorimetry; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D004041:Dietary Fats / Q000378:metabolism; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism; D006801:Humans; D006860:Hydrogen Bonding; D007413:Intestinal Mucosa / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018996:Myelin P2 Protein / Q000737:chemistry* / Q000378:metabolism; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry; D012996:Solutions; D025521:Tumor Suppressor Proteins
chemical_list: D002352:Carrier Proteins; D004041:Dietary Fats; C107608:FABP7 protein, human; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D011994:Recombinant Proteins; D012996:Solutions; D025521:Tumor Suppressor Proteins