Active-Site Dynamics of SpvC Virulence Factor from Salmonella typhimurium and DensityFunctional Theory Study of Phosphothreonine Lyase Catalysis

Document Type

Article

Journal/Book Title

Journal of Physical Chemistry

Publication Date

2009

Volume

113

Issue

46

First Page

15327

Last Page

15333

Abstract

The newly discovered SpvC effector protein from Salmonella typhimurium interferes with the host immune response by dephosphorylating mitogen-activated protein kinases (MAPKs) with a β-elimination mechanism. To understand this unique phosphothreonine lyase catalysis, the dynamics of the enzyme−substrate complex of the SpvC effector is investigated with a 3.2 ns molecular dynamics simulation, which reveals that the phosphorylated peptide substrate is tightly held in the active site by a hydrogen bond network and the lysine general base is positioned for the abstraction of the alpha hydrogen. The catalysis is further modeled with density functional theory (DFT) in a truncated active-site model at the B3LYP/6-31+G(d,p) level of theory. The DFT calculations indicate the reaction proceeds via a single transition state, featuring a concerted proton abstraction from the α-carbon by Lys136 and β-elimination of the phosphate leaving group. Key kinetic isotopic effects are predicted based on the truncated active-site model.

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