Ab initio QM/MM study of class A β-lactamase acylation

Dual participation of Glu166 and Lys73 in a concerted base promotion of Ser70

Samy Meroueh, Jed F. Fisher, H. Bernhard Schlegel, Shahriar Mobashery

Research output: Contribution to journalArticle

102 Citations (Scopus)

Abstract

β-Lactamase acquisition is the most prevalent basis for Gram-negative bacteria resistance to the β-lactam antibiotics. The mechanism used by the most common class A Gram-negative β-lactamases is serine acylation followed by hydrolytic deacylation, destroying the β-lactam. The ab initio quantum mechanical/molecular mechanical (QM/MM) calculations, augmented by extensive molecular dynamics simulations reported herein, describe the serine acylation mechanism for the class A TEM-1 β-lactamase with penicillanic acid as substrate. Potential energy surfaces (based on approximately 350 MP2/6-31+G* calculations) reveal the proton movements that govern Ser70 tetrahedral formation and then collapse to the acyl-enzyme. A remarkable duality of mechanism for tetrahedral formation is implicated. Following substrate binding, the pathway initiates by a low energy barrier (5 kcal mol-1) and an energetically favorable transfer of a proton from Lys73 to Glu166, through the catalytic water molecule and Ser70. This gives unprotonated Lys73 and protonated Glu166. Tetrahedral formation ensues in a concerted general base process, with Lys73 promoting Ser70 addition to the β-lactam carbonyl. Moreover, the three-dimensional potential energy surface also shows that the previously proposed pathway, involving Glu166 as the general base promoting Ser70 through a conserved water molecule, exists in competition with the Lys73 process. The existence of two routes to the tetrahedral species is fully consistent with experimental data for mutant variants of the TEM β-lactamase.

Original languageEnglish (US)
Pages (from-to)15397-15407
Number of pages11
JournalJournal of the American Chemical Society
Volume127
Issue number44
DOIs
StatePublished - Nov 9 2005
Externally publishedYes

Fingerprint

Lactams
Acylation
Potential energy surfaces
Serine
Protons
Penicillanic Acid
Transmission electron microscopy
Molecules
Water
Energy barriers
Antibiotics
Substrates
Molecular Dynamics Simulation
Gram-Negative Bacteria
Molecular dynamics
Bacteria
Enzymes
Anti-Bacterial Agents
Acids
Computer simulation

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Ab initio QM/MM study of class A β-lactamase acylation : Dual participation of Glu166 and Lys73 in a concerted base promotion of Ser70. / Meroueh, Samy; Fisher, Jed F.; Schlegel, H. Bernhard; Mobashery, Shahriar.

In: Journal of the American Chemical Society, Vol. 127, No. 44, 09.11.2005, p. 15397-15407.

Research output: Contribution to journalArticle

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abstract = "β-Lactamase acquisition is the most prevalent basis for Gram-negative bacteria resistance to the β-lactam antibiotics. The mechanism used by the most common class A Gram-negative β-lactamases is serine acylation followed by hydrolytic deacylation, destroying the β-lactam. The ab initio quantum mechanical/molecular mechanical (QM/MM) calculations, augmented by extensive molecular dynamics simulations reported herein, describe the serine acylation mechanism for the class A TEM-1 β-lactamase with penicillanic acid as substrate. Potential energy surfaces (based on approximately 350 MP2/6-31+G* calculations) reveal the proton movements that govern Ser70 tetrahedral formation and then collapse to the acyl-enzyme. A remarkable duality of mechanism for tetrahedral formation is implicated. Following substrate binding, the pathway initiates by a low energy barrier (5 kcal mol-1) and an energetically favorable transfer of a proton from Lys73 to Glu166, through the catalytic water molecule and Ser70. This gives unprotonated Lys73 and protonated Glu166. Tetrahedral formation ensues in a concerted general base process, with Lys73 promoting Ser70 addition to the β-lactam carbonyl. Moreover, the three-dimensional potential energy surface also shows that the previously proposed pathway, involving Glu166 as the general base promoting Ser70 through a conserved water molecule, exists in competition with the Lys73 process. The existence of two routes to the tetrahedral species is fully consistent with experimental data for mutant variants of the TEM β-lactamase.",
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