Structure, Dynamics, and Mechanism of Proteins the MIF Superfamily

The human MIF and MIF-2 (formerly, D-DT) are pro-inflammatory cytokines with a number of distinguishing features. (1) They are homotrimers that agonists of the receptor human CD74. MIF is also a partial agonist of CXCR2 and CXCR4. (2) The three-dimensional structure resembles the microbial isomerase, 5-(carboxymethyl)-2-hydroxymuconate isomerase (CHMI), and a tautomerase, 4-oxalocrotonate tautomerase, with similarities that all of these proteins have enzymatic sites between two subunits of the trimer with the same catalytic residue, a unique Pro-1 with an unusually low pKa that allows it to function as catalytic base. (3) The bona fide substrate for MIF and MIF-2 are yet to be identified, but “substrate mimics” – a non-physiological (D-dopachrome) and physiological (hydroxyphenylpyruvate [HPP]) – were identified that allowed us to perform high throughput screen to identify tool compounds to test these proteins’ other biological activities. (4) MIF has a solvent channel co-incident with its 3-fold axis while MIF-2 has a deep cavity filled with water molecules. Molecular dynamics simulations was applied to MIF and the highest centrality residue (Tyr-99) was found to be an allosteric site effecting the CD74 signaling and the catalytic activity.

MIF and MIF-2 are reported to be involved in multiple diseases, but we are studying an allosteric ligand found in the high throughput screen that inhibits one of the 60 cell lines from the National Cancer Institute. We are also screening for a different allosteric agonist that disrupts Tyr-99 and its effects on the functions of MIF.