3DJY

Nonaged Form of Human Butyrylcholinesterase Inhibited by Tabun

Summary for 3DJY

• Entry DOI: 10.2210/pdb3djy/pdb
• Related: 3DKK 3DL4 3DL7
• Descriptor: Cholinesterase, 2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-[beta-L-fucopyranose-(1-6)]2-acetamido-2-deoxy-beta-D-glucopyranose, beta-L-fucopyranose-(1-6)-2-acetamido-2-deoxy-beta-D-glucopyranose, ... (8 entities in total)
• Functional Keywords: hydrolase, tabun, organophosphate, aging, disease mutation, glycoprotein, serine esterase
• Biological source: Homo sapiens (human)
• Total number of polymer chains: 1
• Total formula weight: 62209.53

Authors

Carletti, E.,Nachon, F. (deposition date: 2008-06-24, release date: 2008-12-02, Last modification date: 2021-10-20)

Primary citation

Carletti, E.,Li, H.,Li, B.,Ekstrom, F.,Nicolet, Y.,Loiodice, M.,Gillon, E.,Froment, M.T.,Lockridge, O.,Schopfer, L.M.,Masson, P.,Nachon, F.
Aging of Cholinesterases Phosphylated by Tabun Proceeds through O-Dealkylation.
J.Am.Chem.Soc., 130:16011-16020, 2008

PubMed Abstract: Human butyrylcholinesterase (hBChE) hydrolyzes or scavenges a wide range of toxic esters, including heroin, cocaine, carbamate pesticides, organophosphorus pesticides, and nerve agents. Organophosphates (OPs) exert their acute toxicity through inhibition of acetylcholinesterase (AChE) by phosphorylation of the catalytic serine. Phosphylated cholinesterase (ChE) can undergo a spontaneous, time-dependent process called "aging", during which the OP-ChE conjugate is dealkylated. This leads to irreversible inhibition of the enzyme. The inhibition of ChEs by tabun and the subsequent aging reaction are of particular interest, because tabun-ChE conjugates display an extraordinary resistance toward most current oxime reactivators. We investigated the structural basis of oxime resistance for phosphoramidated ChE conjugates by determining the crystal structures of the non-aged and aged forms of hBChE inhibited by tabun, and by updating the refinement of non-aged and aged tabun-inhibited mouse AChE (mAChE). Structures for non-aged and aged tabun-hBChE were refined to 2.3 and 2.1 A, respectively. The refined structures of aged ChE conjugates clearly show that the aging reaction proceeds through O-dealkylation of the P(R) enantiomer of tabun. After dealkylation, the negatively charged oxygen forms a strong salt bridge with protonated His438N epsilon2 that prevents reactivation. Mass spectrometric analysis of the aged tabun-inhibited hBChE showed that both the dimethylamine and ethoxy side chains were missing from the phosphorus. Loss of the ethoxy is consistent with the crystallography results. Loss of the dimethylamine is consistent with acid-catalyzed deamidation during the preparation of the aged adduct for mass spectrometry. The reported 3D data will help in the design of new oximes capable of reactivating tabun-ChE conjugates.

PubMed: 18975951
DOI: 10.1021/ja804941z

Experimental method

X-RAY DIFFRACTION (2.1 Å)