OSMOLYTE INDUCED – CONFORMATIONAL CHANGES REVEAL NOVEL METHOD OF PURIFYING APO-INDOLEAMINE 2,3-DIOXYGENASE 1

Abstract

Human indoleamine 2,3-dioxygenase 1 (IDO1) is a heme binding protein responsible for catalyzing the rate determining step of the kynurenine pathway, the conversion of essential amino acid L-tryptophan to N’-formylkynurenine. Given the association between the kynurenine pathway and immunoregulatory function, IDO1 has been identified as a promising therapeutic target to combat immunodeficiency and autoimmune diseases, which has prompted the discovery of different class inhibitors and activators. In the efforts to characterize IDO1 as a model immunoregulator, the Groves Lab has sought to uncover the chemical mechanism and molecular underpinnings of this protein, which remains elusive in the field. Thus, using an elementary and traditional approach, this thesis subjects IDO1 to structural modifications induced by common osmolytes: urea, trimethyl-N’-oxide, betaine, and 2,2,2-trifluoroethanol. By disturbing the protein structure and inducing heme dissociation via osmolytic aggravation, we are able to develop a novel method of purifying apo-IDO1, an infamously difficult, yet biologically relevant, conformation of IDO1.