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Structural Insights from Molecular Dynamics Simulations of Tryptophan 7-Halogenase and Tryptophan 5-Halogenase

Research output: Contribution to journalArticle

  • Jon Ainsley
  • Adrian J. Mulholland
  • Gary W. Black
  • Olivier Sparagano
  • Christo Z. Christov
  • Tatyana G. Karabencheva-Christova
Original languageEnglish
Pages (from-to)4847-4859
Number of pages13
JournalACS Omega
Volume3
Issue number5
Early online date2 May 2018
DOIs
DateAccepted/In press - 24 Apr 2018
DateE-pub ahead of print - 2 May 2018
DatePublished (current) - 31 May 2018

Abstract

Many natural organic compounds with pharmaceutical applications, including antibiotics (chlortetracycline and vancomycin), antifungal compounds (pyrrolnitrin), and chemotherapeutics (salinosporamide A and rebeccamycin) are chlorinated. Halogenating enzymes like tryptophan 7-halogenase (PrnA) and tryptophan 5-halogenase (PyrH) perform regioselective halogenation of tryptophan. In this study, the conformational dynamics of two flavin-dependent tryptophan halogenases - PrnA and PyrH - was investigated through molecular dynamics simulations, which are in agreement with the crystallographic and kinetic experimental studies of both enzymes and provide further explanation of the experimental data at an atomistic level of accuracy. They show that the binding sites of the cofactor-flavin adenine dinucleotide and the substrate do not come into close proximity during the simulations, thus supporting an enzymatic mechanism without a direct contact between them. Two catalytically important active site residues, glutamate (E346/E354) and lysine (K79/K75) in PrnA and PyrH, respectively, were found to play a key role in positioning the proposed chlorinating agent, hypochlorous acid. The changes in the regioselectivity between PrnA and PyrH arise as a consequence of differences in the orientation of substrate in its binding site.

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