Refined apoprotein structure of rat intestinal fatty acid binding protein produced in Escherichia coli | Academic Article individual record

Rat intestinal fatty acid binding protein (I-FABP) is a member of a family of cytoplasmic hydrophobic ligand-binding proteins. To gain insights about the contribution of bound fatty acid to I-FABP's conformation and mechanism of ligand binding, we have determined the structure of Escherichia coli-derived rat apo-I-FABP to 1.96-A resolution and compared it to the recently refined structure of I-FABP with bound palmitate. Both apo- and holo-I-FABP are composed primarily of anti-parallel beta-strands which form two nearly orthogonal beta-sheets (\"beta-clam\"). The overall structures of the apo- and holo-I-FABP are nearly identical, with a root mean square (rms) difference of 0.37 A between C alpha atoms, 0.38 A between all main-chain atoms, and 0.94 A between all side-chain atoms. However, rms differences of greater than 1.3 A were noted for the side chains of Ile-23, Lys-27, Arg-56, Leu-72, Ala-73, and Asp-74. The space occupied by bound ligand in the core of the holoprotein is occupied in the apo-protein by ordered solvent molecules. This results in an increase in the total number of internal ordered solvent molecules from 7 in the holoprotein to 13 in apo-I-FABP. This finding, together with observed differences in the side-chain orientations of two residues (Arg-56 and Lys-27) situated over a potential opening to the cores of the apo- and holoproteins, suggests that solvent molecules play a critical role in ligand binding. Moreover, the data indicate that the beta-clam structure is stable even in the absence of bound ligand.

author list (cited authors)
Sacchettini, J. C., Gordon, J. I., & Banaszak, L. J.
publication date
  • Apoproteins
  • Fatty Acids
  • Carrier Proteins
  • X-Ray Diffraction
  • Protein Conformation
  • Fatty Acid-binding Proteins
  • Crystallization
  • Models, Molecular
  • Neoplasm Proteins
  • Fatty Acid-binding Protein 7
  • Recombinant Proteins
  • Nerve Tissue Proteins
  • Escherichia Coli
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