In silico studies on the role of mutant Y337A to reactivate tabun inhibited mAChE with K048.
Organophosphorus compound (OP) tabun is resistant to reactivate by many oxime drugs after the formation of OP-conjugate with AChE. The reactivation of tabun-inhibited mAChE and site-directed mutants by bispyridinium oxime, K048 (N-[4-(4-hydroxyiminomethylpyridinio)butyl]-4-carbamoylpyridinium dibromide) showed that the mutations significantly poor the overall reactivation efficacy of K048. We have unravelled the lowered efficacy of K048 with the tabun-mutant mAChE(Y337A) using docking and steered molecular dynamics (SMD) simulations. The computed results showed some interesting features for the interaction of drug molecule K048 with tabun-mAChE(wild-type) and tabun-mutant mAChE(Y337A). The SMD simulations showed that the active pyridinium ring of K048 is directed towards the phosphorus atom conjugated to the active serine (SUN203) of tabun-mAChE(wild-type). The cradle shaped residues Tyr337-Phe338 present in the choline binding site stabilize the active pyridinium ring of K048 with π-π interaction and the residue Trp86 involved in T-shaped cation-π interaction. However, in the case of tabun-mutant mAChE(Y337A).K048 conjugate, the replacement of aromatic Tyr337 with the aliphatic alanine unit in the choline binding site, however, loses one of the π-π interaction between the active pyridinium ring of K048 and the Tyr337. The placement of aliphatic alanine unit resulted in the displacement of the side chain of Phe338 towards the His447. Such displacement is causing the inaccessibility of the drug towards the phosphorus atom conjugated to the active serine (SUN203) of tabun-mutant mAChE(Y337A). Furthermore, the unbinding of the K048 with SMD studies showed that the active pyridinium ring of the drug undergoes a complete turn along the gorge axis and is directed away from the phosphorus atom conjugated to the active serine of the tabun-mutant mAChE(Y337A). Such effects inside the gorge of tabun-mutant mAChE(Y337A) would lower the efficacy of the drug molecule (K048) for the reactivation process. The binding free energy computed for the tabun-mAChE(wild-type) and tabun-mutant mAChE(Y337A) with K048 showed that the drug molecule prefers to bind strongly with the former enzyme (∼30 kJ/mol) than the later one.
Computation and Simulation Unit (Analytical Discipline and Centralized Instrument Facility), CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, Gujarat, 364 002, India; Academy of Scientific and Innovative Research, CSIR-CSMCRI, Bhavnagar, Gujarat, 364 002, India.
Nellore Bhanu
NB
Chandar
Computation and Simulation Unit (Analytical Discipline and Centralized Instrument Facility), CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, Gujarat, 364 002, India; Academy of Scientific and Innovative Research, CSIR-CSMCRI, Bhavnagar, Gujarat, 364 002, India.
Shibaji
S
Ghosh
Computation and Simulation Unit (Analytical Discipline and Centralized Instrument Facility), CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, Gujarat, 364 002, India.
Rabindranath
R
Lo
Department of Pure and Applied Chemistry, Ladoke Akintola University of Technology, PMB 4000, Ogbomoso, Oyo State, Nigeria.
Semire
S
Banjo
Computation and Simulation Unit (Analytical Discipline and Centralized Instrument Facility), CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, Gujarat, 364 002, India; Academy of Scientific and Innovative Research, CSIR-CSMCRI, Bhavnagar, Gujarat, 364 002, India. Electronic address: ganguly@csmcri.org.
Bishwajit
B
Ganguly
D000110:Acetylcholinesterase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020134:Catalytic Domain; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D003198:Computer Simulation; D004793:Enzyme Reactivators / Q000378:metabolism / Q000494:pharmacology*; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D009154:Mutation; D010755:Organophosphates / Q000494:pharmacology*; D010091:Oximes / Q000378:metabolism / Q000494:pharmacology*; D011726:Pyridinium Compounds / Q000378:metabolism / Q000494:pharmacology*
C488676:1-(4-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium)butane; D002800:Cholinesterase Inhibitors; D004793:Enzyme Reactivators; D010755:Organophosphates; D010091:Oximes; D011726:Pyridinium Compounds; D000110:Acetylcholinesterase; C009374:tabun
K048; Mutant; Reactivation; Steered molecular dynamics; Tabun; mAChE