title: Ionization state and molecular docking studies for the macrophage migration inhibitory factor: the role of lysine 32 in the catalytic mechanism.
abstract: The macrophage migration inhibitory factor (MIF) is a cytokine that is structurally similar to certain isomerases and for which multiple immune and catalytic roles have been proposed. Different catalytic activities have been reported for MIF, yet the exact mechanism by which MIF acts is not completely known. As a tautomerase, the enzyme uses a general acid-base mechanism of proton transfer in which the amino-terminal proline has been shown to function as the catalytic base. We report the results of molecular docking simulations of macrophage migration inhibitory factor with three substrates, D-dopachrome, L-dopachrome methyl ester and p-(hydroxyphenyl)pyruvate. Electrostatic pK(a) predictions were also performed for the free and complexed forms of the enzyme. The predicted binding mode of p-(hydroxyphenyl)pyruvate is in agreement with the recently published X-ray structure. A model for the binding mode of D-dopachrome and L-dopachrome methyl ester to MIF is proposed which offers insights into the catalytic mechanism of D-dopachrome tautomerase activity of MIF. The proposed catalytic mechanism is further supported by the pK(a) predictions, which suggest that residue Lys32 acts as the general acid for the enzymatic catalysis of D-dopachrome.
authors.affiliation: Department of Biology and Biochemistry, University of Houston, TX 77204-5513, USA.
authors.forename: T
authors.initials: T
authors.lastname: Soares
authors.forename: D
authors.initials: D
authors.lastname: Goodsell
authors.forename: R
authors.initials: R
authors.lastname: Ferreira
authors.forename: A J
authors.initials: AJ
authors.lastname: Olson
authors.forename: J M
authors.initials: JM
authors.lastname: Briggs
mesh_terms: D002384:Catalysis; D020134:Catalytic Domain; D045563:Indolequinones; D007211:Indoles / Q000737:chemistry / Q000378:metabolism; D008239:Lysine; D008263:Macrophage Migration-Inhibitory Factors / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D011809:Quinones / Q000737:chemistry / Q000378:metabolism; D055672:Static Electricity
chemical_list: D045563:Indolequinones; D007211:Indoles; D008263:Macrophage Migration-Inhibitory Factors; D011809:Quinones; C001123:dopachrome; D008239:Lysine