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| [[Image:3chb.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_3chb| PDB=3chb | SCENE= }} | | {{STRUCTURE_3chb| PDB=3chb | SCENE= }} |
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| '''CHOLERA TOXIN B-PENTAMER COMPLEXED WITH GM1 PENTASACCHARIDE'''
| | ===CHOLERA TOXIN B-PENTAMER COMPLEXED WITH GM1 PENTASACCHARIDE=== |
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| ==Overview==
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| Crystals of the 61 kDa complex of the cholera toxin B-pentamer with the ganglioside GM1 receptor pentasaccharide diffract to near-atomic resolution. We have refined the crystallographic model for this complex using anisotropic displacement parameters for all atoms to a conventional crystallographic residual R=0.129 for all observed Bragg reflections in the resolution range 22 A to 1.25 A. Remarkably few residues show evidence of discrete conformational disorder. A notable exception is a minority conformation found for the Cys9 side-chain, which implies that the Cys9-Cys86 disulfide linkage is incompletely formed. In all five crystallographically independent instances, the peptide backbone in the region of the receptor-binding site shows evidence of strain, including unusual bond lengths and angles, and a highly non-planar (omega=153.7(7) degrees) peptide group between residues Gln49 and Val50. The location of well-ordered water molecules at the protein surface is notable reproduced among the five crystallographically independent copies of the peptide chain, both at the receptor-binding site and elsewhere. The 5-fold non-crystallographic symmetry of this complex allows an evaluation of the accuracy, reproducibility, and derived error estimates from refinement of large structures at near-atomic resolution. We find that blocked-matrix treatment of parameter covariance underestimates the uncertainty of atomic positions in the final model by approximately 10% relative to estimates based either on full-matrix inversion or on the 5-fold non-crystallographic symmetry.
| | The line below this paragraph, {{ABSTRACT_PUBMED_9753553}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 9753553 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_9753553}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Toxin]] | | [[Category: Toxin]] |
| [[Category: Toxin/receptor complex]] | | [[Category: Toxin/receptor complex]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 21:46:41 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 08:03:11 2008'' |
