1A57

THE THREE-DIMENSIONAL STRUCTURE OF A HELIX-LESS VARIANT OF INTESTINAL FATTY ACID BINDING PROTEIN, NMR, 20 STRUCTURES

Summary for 1A57

• Entry DOI: 10.2210/pdb1a57/pdb
• Descriptor: INTESTINAL FATTY ACID-BINDING PROTEIN (1 entity in total)
• Functional Keywords: fatty acid-binding, lipid transport, beta-clam, lipocalins
• Biological source: Rattus norvegicus (Norway rat)
• Cellular location: Cytoplasm: P02693
• Total number of polymer chains: 1
• Total formula weight: 13164.65

Authors

Steele, R.A.,Emmert, D.A.,Kao, J.,Hodsdon, M.E.,Frieden, C.,Cistola, D.P. (deposition date: 1998-02-20, release date: 1998-05-27, Last modification date: 2024-05-22)

Primary citation

Steele, R.A.,Emmert, D.A.,Kao, J.,Hodsdon, M.E.,Frieden, C.,Cistola, D.P.
The three-dimensional structure of a helix-less variant of intestinal fatty acid-binding protein.
Protein Sci., 7:1332-1339, 1998

PubMed Abstract: Intestinal fatty acid-binding protein (I-FABP) is a cytosolic 15.1-kDa protein that appears to function in the intracellular transport and metabolic trafficking of fatty acids. It binds a single molecule of long-chain fatty acid in an enclosed cavity surrounded by two five-stranded antiparallel beta-sheets and a helix-turn-helix domain. To investigate the role of the helical domain, we engineered a variant of I-FABP by deleting 17 contiguous residues and inserting a Ser-Gly linker (Kim K et al., 1996, Biochemistry 35:7553-7558). This variant, termed delta17-SG, was remarkably stable, exhibited a high beta-sheet content and was able to bind fatty acids with some features characteristic of the wild-type protein. In the present study, we determined the structure of the delta17-SG/palmitate complex at atomic resolution using triple-resonance 3D NMR methods. Sequence-specific 1H, 13C, and 15N resonance assignments were established at pH 7.2 and 25 degrees C and used to define the consensus 1H/13C chemical shift-derived secondary structure. Subsequently, an iterative protocol was used to identify 2,544 NOE-derived interproton distance restraints and to calculate its tertiary structure using a unique distance geometry/simulated annealing algorithm. In spite of the sizable deletion, the delta17-SG structure exhibits a backbone conformation that is nearly superimposable with the beta-sheet domain of the wild-type protein. The selective deletion of the alpha-helical domain creates a very large opening that connects the interior ligand-binding cavity with exterior solvent. Unlike wild-type I-FABP, fatty acid dissociation from delta17-SG is structurally and kinetically unimpeded, and a protein conformational transition is not required. The delta17-SG variant of I-FABP is the only wild-type or engineered member of the intracellular lipid-binding protein family whose structure lacks alpha-helices. Thus, delta17-SG I-FABP constitutes a unique model system for investigating the role of the helical domain in ligand-protein recognition, protein stability and folding, lipid transfer mechanisms, and cellular function.

PubMed: 9655337

Experimental method

SOLUTION NMR