2b4m

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Crystal structure of the binding protein OpuAC in complex with proline betaine

Structural highlights

2b4m is a 2 chain structure with sequence from Bacillus subtilis. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:X-ray diffraction, Resolution 2.8Å
Ligands:PBE
Resources:FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

OPUAC_BACSU Involved in a multicomponent binding-protein-dependent transport system for glycine betaine.[1] [2]

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

Publication Abstract from PubMed

Compatible solutes play a decisive role in the defense of microorganisms against changes in temperature and increases in osmolarity in their natural habitats. In Bacillus subtilis, the substrate-binding protein (SBP)-dependent ABC-transporter OpuA serves for the uptake of the compatible solutes glycine betaine (GB) and proline betaine (PB). Here, we report the determinants of compatible solute binding by OpuAC, the SBP of the OpuA transporter, by equilibrium binding studies and X-ray crystallography. The affinity of OpuAC/GB and OpuAC/PB complexes were analyzed by intrinsic tryptophan fluorescence and the K(D) values were determined to be 17(+/-1)microM for GB and 295(+/-27)microM for PB, respectively. The structures of OpuAC in complex with GB or PB were solved at 2.0 A and 2.8 A, respectively, and show an SBP-typical class II fold. The ligand-binding pocket is formed by three tryptophan residues arranged in a prism-like geometry suitable to coordinate the positive charge of the trimethyl ammonium group of GB and the dimethyl ammonium group of PB by cation-pi interactions and by hydrogen bonds with the carboxylate moiety of the ligand. Structural differences between the OpuAC/GB and OpuAC/PB complexes occur within the ligand-binding pocket as well as across the domain-domain interface. These differences provide a structural framework to explain the drastic differences in affinity of the OpuAC/GB and OpuAC/PB complexes. A sequence comparison with putative SBP specific for compatible solutes reveals the presence of three distinct families for which the crystal structure of OpuAC might serve as a suitable template to predict the structures of these putative compatible solute-binding proteins.

Molecular determinants for substrate specificity of the ligand-binding protein OpuAC from Bacillus subtilis for the compatible solutes glycine betaine and proline betaine.,Horn C, Sohn-Bosser L, Breed J, Welte W, Schmitt L, Bremer E J Mol Biol. 2006 Mar 24;357(2):592-606. Epub 2006 Jan 13. PMID:16445940[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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See Also

References

  1. ↑ Kempf B, Bremer E. OpuA, an osmotically regulated binding protein-dependent transport system for the osmoprotectant glycine betaine in Bacillus subtilis. J Biol Chem. 1995 Jul 14;270(28):16701-13. PMID:7622480
  2. ↑ Kappes RM, Kempf B, Bremer E. Three transport systems for the osmoprotectant glycine betaine operate in Bacillus subtilis: characterization of OpuD. J Bacteriol. 1996 Sep;178(17):5071-9. PMID:8752321
  3. ↑ Horn C, Sohn-Bosser L, Breed J, Welte W, Schmitt L, Bremer E. Molecular determinants for substrate specificity of the ligand-binding protein OpuAC from Bacillus subtilis for the compatible solutes glycine betaine and proline betaine. J Mol Biol. 2006 Mar 24;357(2):592-606. Epub 2006 Jan 13. PMID:16445940 doi:10.1016/j.jmb.2005.12.085

Contents


PDB ID 2b4m

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