The three-dimensional structure of a ligand-free closed form of the glucose/galactose binding protein from Salmonella typhimurium has been determined at a resolution of 1.9 A. The crystallographic R-factor for the refined structure is 17.9%. The model contains all the atoms of the 309 residues of the protein sequence, a calcium ion, and 174 water molecules ...
The three-dimensional structure of a ligand-free closed form of the glucose/galactose binding protein from Salmonella typhimurium has been determined at a resolution of 1.9 A. The crystallographic R-factor for the refined structure is 17.9%. The model contains all the atoms of the 309 residues of the protein sequence, a calcium ion, and 174 water molecules. The root mean square (r.m.s.) deviations for the whole molecule are: 0.010 A for bond lengths and 2.44 degrees for bond angles, indicating a good stereochemistry for the model. This structure shows that the protein is able to close in the absence of ligand, adopting a conformation similar to the liganded form but slightly more open. Water molecules satisfy the hydrogen bonding ability of the hydrophilic side chains of the binding site in a manner which is reminiscent of the sugars' hydrogen-bonding patterns. Since packing forces are weak, the crystallization event is unlikely to trigger a change from an open to a closed conformation. Instead, the latter must be one of the species in equilibrium in solution which is selected by packing in the crystal lattice.
Related Citations:
The 1.7 Angstroms Refined X-Ray Structure of the Periplasmic Glucose(Slash)Galactose Receptor from Salmonella Typhimurium Zou, J.-Y., Flocco, M.M., Mowbray, S.L. (1993) J Mol Biol 233: 739
Ribose and Glucose-Galactose Receptors Competitors in Bacterial Chemotaxis Mowbray, S.L. (1992) J Mol Biol 227: 418
Structure of the Periplasmic Glucose(Slash)Galactose Receptor of Salmonella Typhimurium Mowbray, S.L., Smith, R.D., Cole, L.B. (1990) Receptor 1: 41
Preliminary X-Ray Data for the Galactose Binding Protein from Salmonella Typhimurium Alber, T., Fahnestock, M., Mowbray, S.L., Petsko, G.A. (1981) J Mol Biol 147: 471
Organizational Affiliation:
Department of Molecular Biology, Swedish University of Agricultural Sciences, Uppsala Biomedical Center.
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