Methyltetrahydrofolate:corrinoid/iron-sulfur Protein Methyltransferase (MeTr): Protonation State of the Ligand and Active-Site Residues
dc.contributor.author | Alonso, Hernan | |
dc.contributor.author | Cummins, Peter | |
dc.contributor.author | Gready, Jill | |
dc.date.accessioned | 2015-12-10T21:53:43Z | |
dc.date.issued | 2009 | |
dc.date.updated | 2016-02-24T10:26:57Z | |
dc.description.abstract | Methyltetrahydrofolate:corrinoid/iron-sulfur protein methyltransferase (MeTr) catalyzes the transfer of the N5-methyl group from N5- methyltetrahydrofolate (CH3THF) to the cobalt center of a corrinoid/iron-sulfur protein, a reaction similar to that of cobalamin-dependent methionine synthase (MetH). For such a reaction to occur, CH3THF is expected to be activated by a stereospecific protonation at the N5 position. It has been shown experimentally that binding to MeTr is associated with a pK a increase and proton uptake. The enzyme could achieve this by binding the unprotonated form of CH3THF, followed by specific protonation at the correct orientation. Here we have used computational approaches to investigate the protonation state of the ligand and active-site residues in MeTr. First, quantum mechanical (QM) methods with the PCM solvation model were used to predict protonation positions and pKa values of pterin, folate, and their analogues in an aqueous environment. After a reliable calibration of computational and experimental results was obtained, the effect of the protein environment was then considered. Different protonation states of CH3THF and activesite aspartic residues (D75 and D160) were investigated using QM calculations of active-site fragment complexes and the perturbed quantum atom (PQA) approach within QM/MM simulations. The final free energy results indicate that the N5 position of the tetrahydropterin ring is the preferred protonation position of CH3THF when bound to the active site of MeTr, followed by Asp160. We also found that the active-site environment is likely to increase the pKa of N5 by about 3 units, leading to proton uptake upon CH3THF binding, as observed experimentally for MeTr. Some implications of the results are discussed for the MetH mechanism. | |
dc.identifier.issn | 1520-6106 | |
dc.identifier.uri | http://hdl.handle.net/1885/38619 | |
dc.publisher | American Chemical Society | |
dc.source | Journal of Physical Chemistry B | |
dc.subject | Keywords: Active site; Aqueous environment; Computational approach; Methionine synthase; Methyl group; Methyltransferases; Proton uptake; Protonation state; Quantum atoms; Quantum mechanical method; Site environments; Solvation models; Stereospecific; Binding energ | |
dc.title | Methyltetrahydrofolate:corrinoid/iron-sulfur Protein Methyltransferase (MeTr): Protonation State of the Ligand and Active-Site Residues | |
dc.type | Journal article | |
local.bibliographicCitation.issue | 44 | |
local.bibliographicCitation.lastpage | 96 | |
local.bibliographicCitation.startpage | 14787 | |
local.contributor.affiliation | Alonso, Hernan, College of Medicine, Biology and Environment, ANU | |
local.contributor.affiliation | Cummins, Peter, College of Medicine, Biology and Environment, ANU | |
local.contributor.affiliation | Gready, Jill, College of Medicine, Biology and Environment, ANU | |
local.contributor.authoremail | u9508363@anu.edu.au | |
local.contributor.authoruid | Alonso, Hernan, u3999873 | |
local.contributor.authoruid | Cummins, Peter, u9508363 | |
local.contributor.authoruid | Gready, Jill, u9508375 | |
local.description.embargo | 2037-12-31 | |
local.description.notes | Imported from ARIES | |
local.identifier.absfor | 030799 - Theoretical and Computational Chemistry not elsewhere classified | |
local.identifier.absfor | 030701 - Quantum Chemistry | |
local.identifier.absfor | 060107 - Enzymes | |
local.identifier.ariespublication | u4020362xPUB164 | |
local.identifier.citationvolume | 133 | |
local.identifier.doi | 10.1021/jp900181g | |
local.identifier.scopusID | 2-s2.0-72449124231 | |
local.identifier.thomsonID | 000271105600031 | |
local.identifier.uidSubmittedBy | u4020362 | |
local.type.status | Published Version |
Downloads
Original bundle
1 - 1 of 1
No Thumbnail Available
- Name:
- 01_Alonso_Methyltetrahydrofolate:corrinoi_2009.pdf
- Size:
- 383.15 KB
- Format:
- Adobe Portable Document Format