5FPP

Structure of a pre-reaction ternary complex between sarin- acetylcholinesterase and HI-6

Summary for 5FPP

• Entry DOI: 10.2210/pdb5fpp/pdb
• Related: 5FOQ 5FPQ
• Descriptor: ACETYLCHOLINESTERASE, 2-acetamido-2-deoxy-beta-D-glucopyranose, CARBONATE ION, ... (7 entities in total)
• Functional Keywords: hydrolase, sarin, hi-6, qm, density functional theory calculations, michaelis complex.
• Biological source: MUS MUSCULUS (HOUSE MOUSE)
• Total number of polymer chains: 2
• Total formula weight: 122176.65

Authors

Allgardsson, A.,Berg, L.,Akfur, C.,Hornberg, A.,Worek, F.,Linusson, A.,Ekstrom, F. (deposition date: 2015-12-02, release date: 2016-05-11, Last modification date: 2024-01-10)

Primary citation

Allgardsson, A.,Berg, L.,Akfur, C.,Hornberg, A.,Worek, F.,Linusson, A.,Ekstrom, F.J.
Structure of a Prereaction Complex between the Nerve Agent Sarin, its Biological Target Acetylcholinesterase, and the Antidote Hi-6.
Proc.Natl.Acad.Sci.USA, 113:5514-, 2016

PubMed Abstract: 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.

PubMed: 27140636
DOI: 10.1073/PNAS.1523362113

Experimental method

X-RAY DIFFRACTION (2.4 Å)