Probing the role of amino acids in oxime-mediated reactivation of nerve agent-inhibited human acetylcholinesterase

Chambers, Carolyn; Luo, Chunyuan; Tang, Min; Yang, Yerie; Saxena, Ashima

doi:10.1016/j.tiv.2014.11.001

Cited by 10 publications

(8 citation statements)

References 34 publications

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“…The significant reduction of the rate constant supports the hypothesis that Glu202 stabilizes the adduct in an oxime-accessible conformation, whereas the small effect on the dissociation constant indicates that Glu202 does not directly influence the binding of HI-6. These findings are consistent with the 3min HI-6•sarin-mAChE structure and earlier studies of Glu202 substitutions (25,28).…”

Section: Reactivation Kinetics Measurements Show the Importance Of Glsupporting

confidence: 92%

“…The structural and kinetic data for the 3min HI-6•sarin-mAChE complex presented herein suggest a prereaction complex that agree with previously reported reactivation kinetics of site-directed mutants (ref. 25 and references therein) (Movie S1). Furthermore, in conjunction with the previously reported structures, the prereaction complex makes it possible to identify many of the chemical species and conformational changes that are involved in the reactivation cycle (Fig.…”

Section: Reactivation Kinetics Measurements Show the Importance Of Glmentioning

confidence: 99%

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Structure of a prereaction complex between the nerve agent sarin, its biological target acetylcholinesterase, and the antidote HI-6

Allgardsson

Berg

Akfur

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Organophosphorus nerve agents interfere with cholinergic signaling by covalently binding to the active site of the enzyme acetylcholinesterase (AChE). This inhibition causes an accumulation of the neurotransmitter acetylcholine, potentially leading to overstimulation of the nervous system and death. Current treatments include the use of antidotes that promote the release of functional AChE by an unknown reactivation mechanism. We have used diffusion trap cryocrystallography and density functional theory (DFT) calculations to determine and analyze prereaction conformers of the nerve agent antidote HI-6 in complex with Mus musculus AChE covalently inhibited by the nerve agent sarin. These analyses reveal previously unknown conformations of the system and suggest that the cleavage of the covalent enzyme-sarin bond is preceded by a conformational change in the sarin adduct itself. Together with data from the reactivation kinetics, this alternate conformation suggests a key interaction between Glu202 and the O-isopropyl moiety of sarin. Moreover, solvent kinetic isotope effect experiments using deuterium oxide reveal that the reactivation mechanism features an isotope-sensitive step. These findings provide insights into the reactivation mechanism and provide a starting point for the development of improved antidotes. The work also illustrates how DFT calculations can guide the interpretation, analysis, and validation of crystallographic data for challenging reactive systems with complex conformational dynamics.acetylcholinesterase | density functional theory | crystallography | nerve agent | reactivation

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Section: Reactivation Kinetics Measurements Show the Importance Of Glsupporting

confidence: 92%

Section: Reactivation Kinetics Measurements Show the Importance Of Glmentioning

confidence: 99%

Structure of a prereaction complex between the nerve agent sarin, its biological target acetylcholinesterase, and the antidote HI-6

Allgardsson

Berg

Akfur

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…The nearby Glu202, which has been previously implicated in the process, appears to interface electrostatically with His447, perhaps assisting in placing His447 in a catalytically relevant position (Figure 1 b). 32,48 In keeping with previous models including the recent DFT computationally derived model, the attack of the oxime likely creates a bipyramidal trigonal intermediate. 27,28 As the bipyramidal trigonal complex collapses, Ser203 deprotonates His447, restoring the native catalytic triad arrangement with a phosphonylated HI-6 product.…”

Section: Chemical Research In Toxicologymentioning

confidence: 54%

Structural Insights of Stereospecific Inhibition of Human Acetylcholinesterase by VX and Subsequent Reactivation by HI-6

Bester

Guelta

Cheung

et al. 2018

Chem. Res. Toxicol.

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Over 50 years ago, the toxicity of irreversible organophosphate inhibitors targeting human acetylcholinesterase (hAChE) was observed to be stereospecific. The therapeutic reversal of hAChE inhibition by reactivators has also been shown to depend on the stereochemistry of the inhibitor. To gain clarity on the mechanism of stereospecific inhibition, the X-ray crystallographic structures of hAChE inhibited by a racemic mixture of VX (P R/S ) and its enantiomers were obtained. Beyond identifying hAChE structural features that lend themselves to stereospecific inhibition, structures of the reactivator HI-6 bound to hAChE inhibited by VX enantiomers of varying toxicity, or in its uninhibited state, were obtained. Comparison of hAChE in these pre-reactivation and post-reactivation states along with enzymatic data reveals the potential influence of unproductive reactivator poses on the efficacy of these types of therapeutics. The recognition of structural features related to hAChE’s stereospecificity toward VX shed light on the molecular influences of toxicity and their effect on reactivators. In addition to providing a better understanding of the innate issues with current reactivators, an avenue for improvement of reactivators is envisioned.

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“…hAChE and TcAChE have a high structural identity (∼53%) with a very low root-mean-square deviation (∼1 Å). The catalytic triad (Ser203-His447-Glu334) of hAChE is surrounded by three subsites that are important for catalytic activity 30 : (1) the esteratic subsite or choline-binding site (ES) consists of aromatic residues (Trp86, Tyr133, Tyr337, and Phe338), which bind to the quaternary trimethylammonium moiety of the choline group in the substrate for optimal positioning of the carbonyl carbon in the ester at the acylation site. The catalytic process is facilitated by orientation of the substrate’s carbonyl oxygen toward the oxyanion hole formed by the hydrogens from Gly120, Gly121, and Ala204; (2) the anionic subsite or acyl pocket (AS) of AChE formed by the side chains of Phe295 and Phe297 is the binding pocket for the acyl group of the substrate or the methyl group of methylphosphonate; (3) the PAS, which plays a significant role in excess substrate concentration kinetics, is located at the rim of the gorge and consists of residues including Tyr72, Asp74, Tyr124, Trp286, and Tyr341.…”

Section: Structural Biology Of Acetylcholinesterasementioning

confidence: 99%

Novel multitarget-directed tacrine derivatives as potential candidates for the treatment of Alzheimer’s disease

Dai

et al. 2017

Journal of Enzyme Inhibition and Medicinal Chemistry

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Alzheimer’s disease (AD) is a neurodegenerative disorder, which is complex and progressive; it has not only threatened the health of elderly people, but also burdened the whole social medical and health system. The available therapy for AD is limited and the efficacy remains unsatisfactory. In view of the prevalence and expected increase in the incidence of AD, the design and development of efficacious and safe anti-AD agents has become a hotspot in the field of pharmaceutical research. Due to the multifactorial etiology of AD, the multitarget-directed ligands (MTDLs) approach is promising in search for new drugs for AD. Tacrine, which is the first acetylcholinesterase (AChE) inhibitor, has been selected as the ideal active fragment because of its simple structure, clear activity, and its superiority in the structural modification, thus it could be introduced into the overall molecular skeletons of the multi-target-directed anti-AD agents. In this review, we have summarized the recent advances (2012 to the present) in the chemical modification of tacrine, which could provide the reference for the further study of novel multi-target-directed tacrine derivatives to treat AD.

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Probing the role of amino acids in oxime-mediated reactivation of nerve agent-inhibited human acetylcholinesterase

Cited by 10 publications

References 34 publications

Structure of a prereaction complex between the nerve agent sarin, its biological target acetylcholinesterase, and the antidote HI-6

Structure of a prereaction complex between the nerve agent sarin, its biological target acetylcholinesterase, and the antidote HI-6

Structural Insights of Stereospecific Inhibition of Human Acetylcholinesterase by VX and Subsequent Reactivation by HI-6

Novel multitarget-directed tacrine derivatives as potential candidates for the treatment of Alzheimer’s disease

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