2J4C image
Entry Detail
PDB ID:
2J4C
Keywords:
Title:
Structure of human Butyrylcholinesterase in complex with 10mM HgCl2
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2006-08-28
Release Date:
2007-03-27
Method Details:
Experimental Method:
Resolution:
2.75 Å
R-Value Free:
0.23
R-Value Work:
0.18
R-Value Observed:
0.18
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
CSS A CYS S-MERCAPTOCYSTEINE
Primary Citation
Mechanisms of Cholinesterase Inhibition by Inorganic Mercury.
FEBS J. 274 1849 ? (2007)
PMID: 17355286 DOI: 10.1111/J.1742-4658.2007.05732.X

Abstact

The poorly known mechanism of inhibition of cholinesterases by inorganic mercury (HgCl2) has been studied with a view to using these enzymes as biomarkers or as biological components of biosensors to survey polluted areas. The inhibition of a variety of cholinesterases by HgCl2 was investigated by kinetic studies, X-ray crystallography, and dynamic light scattering. Our results show that when a free sensitive sulfhydryl group is present in the enzyme, as in Torpedo californica acetylcholinesterase, inhibition is irreversible and follows pseudo-first-order kinetics that are completed within 1 h in the micromolar range. When the free sulfhydryl group is not sensitive to mercury (Drosophila melanogaster acetylcholinesterase and human butyrylcholinesterase) or is otherwise absent (Electrophorus electricus acetylcholinesterase), then inhibition occurs in the millimolar range. Inhibition follows a slow binding model, with successive binding of two mercury ions to the enzyme surface. Binding of mercury ions has several consequences: reversible inhibition, enzyme denaturation, and protein aggregation, protecting the enzyme from denaturation. Mercury-induced inactivation of cholinesterases is thus a rather complex process. Our results indicate that among the various cholinesterases that we have studied, only Torpedo californica acetylcholinesterase is suitable for mercury detection using biosensors, and that a careful study of cholinesterase inhibition in a species is a prerequisite before using it as a biomarker to survey mercury in the environment.

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