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Title: Internal Dynamics and Ionization States of the Macrophage Migration Inhibitory Factor: Comparison Between Wild-Type and Mutant Forms

Abstract

The macrophage migration inhibitory factor (MIF) is a cytokine which shares a common structural architecture and catalytic strategy with three isomerases: 4-oxalocrotonate tautomerase, 5-carboxymethyl-2-hydroxymuconate isomerase and D-dopachrome tautomerase. A highly conserved N-terminal proline acts as a base\acid during the proton transfer reaction catalyzed by these enzymes. Such unusual catalytic strategy appears to be possible only due to the N-terminal proline pKa be shifted to 5.0-6.0 units. Mutations of this residue result in a significant decrease of the catalytic activity of MIF. Two hypotheses have been proposed to explain the catalytic inefficiency of MIF: the lower basicity of primary amines with regard to secondary ones and the increased flexibility resulting from the replacement of a proline by residues like glycine. To investigate that, we have performed molecular dynamics simulations of MIF-wt and its mutant P1G as well as calculated the protonation properties of several mutant forms. It has been found that the N-terminal glycine does not show larger fluctuations compared to proline, but the former residue is more exposed to the solvent throughout the simulations. The apparent pKa of these residues displays very little change (as expected from the structural rigidity of MIF) and is not significantly affected by the surroundingmore » ionizable residues. Instead, the hydrophobic character of the active site seems to be the main factor in determining the pKa of the N-terminal residue and the catalytic efficiency of MIF.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
15002933
Report Number(s):
PNNL-SA-36266
KP1303000; TRN: US200322%%240
DOE Contract Number:  
AC06-76RL01830
Resource Type:
Journal Article
Journal Name:
Biopolymers, 65(4):313-323
Additional Journal Information:
Journal Volume: 65; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; AMINES; ENZYMES; GLYCINE; IONIZATION; ISOMERASES; LYMPHOKINES; MACROPHAGES; MUTANTS; MUTATIONS; PROLINE; PROTONS; RESIDUES; SOLVENTS; TRANSFER REACTIONS; Molecular Dynamics; Poisson-Boltzmann Electrostatics; Catalytic Mechanism.

Citation Formats

Soares, Thereza A., Lins, Roberto D., Straatsma, TP, and Briggs, J. M. Internal Dynamics and Ionization States of the Macrophage Migration Inhibitory Factor: Comparison Between Wild-Type and Mutant Forms. United States: N. p., 2002. Web. doi:10.1002/bip.10252.
Soares, Thereza A., Lins, Roberto D., Straatsma, TP, & Briggs, J. M. Internal Dynamics and Ionization States of the Macrophage Migration Inhibitory Factor: Comparison Between Wild-Type and Mutant Forms. United States. doi:10.1002/bip.10252.
Soares, Thereza A., Lins, Roberto D., Straatsma, TP, and Briggs, J. M. Fri . "Internal Dynamics and Ionization States of the Macrophage Migration Inhibitory Factor: Comparison Between Wild-Type and Mutant Forms". United States. doi:10.1002/bip.10252.
@article{osti_15002933,
title = {Internal Dynamics and Ionization States of the Macrophage Migration Inhibitory Factor: Comparison Between Wild-Type and Mutant Forms},
author = {Soares, Thereza A. and Lins, Roberto D. and Straatsma, TP and Briggs, J. M.},
abstractNote = {The macrophage migration inhibitory factor (MIF) is a cytokine which shares a common structural architecture and catalytic strategy with three isomerases: 4-oxalocrotonate tautomerase, 5-carboxymethyl-2-hydroxymuconate isomerase and D-dopachrome tautomerase. A highly conserved N-terminal proline acts as a base\acid during the proton transfer reaction catalyzed by these enzymes. Such unusual catalytic strategy appears to be possible only due to the N-terminal proline pKa be shifted to 5.0-6.0 units. Mutations of this residue result in a significant decrease of the catalytic activity of MIF. Two hypotheses have been proposed to explain the catalytic inefficiency of MIF: the lower basicity of primary amines with regard to secondary ones and the increased flexibility resulting from the replacement of a proline by residues like glycine. To investigate that, we have performed molecular dynamics simulations of MIF-wt and its mutant P1G as well as calculated the protonation properties of several mutant forms. It has been found that the N-terminal glycine does not show larger fluctuations compared to proline, but the former residue is more exposed to the solvent throughout the simulations. The apparent pKa of these residues displays very little change (as expected from the structural rigidity of MIF) and is not significantly affected by the surrounding ionizable residues. Instead, the hydrophobic character of the active site seems to be the main factor in determining the pKa of the N-terminal residue and the catalytic efficiency of MIF.},
doi = {10.1002/bip.10252},
journal = {Biopolymers, 65(4):313-323},
number = 4,
volume = 65,
place = {United States},
year = {2002},
month = {11}
}