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New Insights into Active Site Conformation Dynamics of E. coli PNP Revealed by Combined HD Exchange Approach and Molecular Dynamics Simulations.

Kazazić, Saša and Bertoša, Branimir and Luić, Marija and Mikleušević, Goran and Krzysztof, Tarnowski and Dadlez, Michal and Narczyk, Marta and Bzowska, Agnieszka (2015) New Insights into Active Site Conformation Dynamics of E. coli PNP Revealed by Combined HD Exchange Approach and Molecular Dynamics Simulations. Journal of the American Society for Mass Spectrometry, 27 (1). pp. 73-82.

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Official URL: http://link.springer.com/article/10.1007%2Fs13361-...

Abstract

The biologically active form of purine nucleoside phosphorylase (PNP) from Escherichia coli (EC 2.4.2.1) is a homohexamer unit, assembled as a trimer of dimers. Upon binding of phosphate, neighboring monomers adopt different active site conformations, described as open and closed. To get insight into the functions of the two distinctive active site conformations, virtually inactive Arg24Ala mutant is complexed with phosphate; all active sites are found to be in the open conformation. To understand how the sites of neighboring monomers communicate with each other, we have combined H/D exchange (H/DX) experiments with molecular dynamics (MD) simulations. Both methods point to the mobility of the enzyme, associated with a few flexible regions situated at the surface and within the dimer interface. Although H/DX provides an average extent of deuterium uptake for all six hexamer active sites, it was able to indicate the dynamic mechanism of cross-talk between monomers, allostery. Using this technique, it was found that phosphate binding to the wild type (WT) causes arrest of the molecular motion in backbone fragments that are flexible in a ligand-free state. This was not the case for the Arg24Ala mutant. Upon nucleoside substrate/inhibitor binding, some release of the phosphate-induced arrest is observed for the WT, whereas the opposite effects occur for the Arg24Ala mutant. MD simulations confirmed that phosphate is bound tightly in the closed active sites of the WT; conversely, in the open conformation of the active site of the WT phosphate is bound loosely moving towards the exit of the active site. In Arg24Ala mutant binary complex Pi is bound loosely, too.

Item Type:Article
Subjects:Q Science > Q Science (General)
Divisions:Mass Spectrometry Laboratory
ID Code:1090
Deposited By: Krzysztof Tarmowski
Deposited On:23 Dec 2015 10:10
Last Modified:08 Mar 2018 15:33

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