2XMB image
Entry Detail
PDB ID:
2XMB
Keywords:
Title:
G117H mutant of human butyrylcholinesterase in complex with sulfate
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2010-07-27
Release Date:
2010-12-01
Method Details:
Experimental Method:
Resolution:
2.10 Å
R-Value Free:
0.20
R-Value Work:
0.16
R-Value Observed:
0.16
Space Group:
I 4 2 2
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:CHOLINESTERASE
Mutations:YES
Chain IDs:A
Chain Length:529
Number of Molecules:1
Biological Source:HOMO SAPIENS
Modified Residue
Compound ID Chain ID Parent Comp ID Details 2D Image
ASN A ASN GLYCOSYLATION SITE
Primary Citation
X-Ray Crystallographic Snapshots of Reaction Intermediates in the G117H Mutant of Human Butyrylcholinesterase, a Nerve Agent Target Engineered Into a Catalytic Bioscavenge
Biochem.J. 434 73 ? (2011)
PMID: 21091433 DOI: 10.1042/BJ20101648

Abstact

OPs (organophosphylates) exert their acute toxicity through inhibition of acetylcholinesterase, by phosphylation of the catalytic serine residue. Engineering of human butyrylcholinesterase, by substitution of a histidine residue for the glycine residue at position 117, led to the creation of OP hydrolase activity. However, the lack of structural information and poor understanding of the hydrolytic mechanism of the G117H mutant has hampered further improvements in the catalytic activity. We have solved the crystallographic structure of the G117H mutant with a variety of ligands in its active site. A sulfate anion bound to the active site suggested the positioning for an OP prior to phosphylation. A fluoride anion was found in the active site when NaF was added to the crystallization buffer. In the fluoride complex, the imidazole ring from the His117 residue was substantially shifted, adopting a relaxed conformation probably close to that of the unliganded mutant enzyme. Additional X-ray structures were obtained from the transient covalent adducts formed upon reaction of the G117H mutant with the OPs echothiophate and VX [ethyl ({2-[bis(propan-2-yl)amino]ethyl}sulfanyl](methyl)phosphinate]. The position of the His117 residue shifted in response to the introduction of these adducts, overlaying the phosphylserine residue. These structural data suggest that the dephosphylation mechanism involves either a substantial conformational change of the His117 residue or an adjacent nucleophilic substitution by water.

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Primary Citation of related structures