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Structural Studies of DsbA and its Putative Partner, VKOR, in Mycobacterium tuberculosis
Katie P. Nguyen
Mentor: Celia Goulding
Disulfide bond-forming (Dsb) proteins are essential for the correct folding and disulfide bond formation of
secreted proteins. In Mycobacterium tuberculosis, DsbA is proposed to be a disulfide isomerase and is believed to
be re-oxidized by its putative partner, vitamin K epoxide reductase (VKOR). The intent of this study is to
further investigate the molecular determinants of the interactions between DsbA and VKOR by X-ray
crystallography. In order to achieve this, DsbA crystals were grown in order to be soaked with a VKOR
heptapeptide that binds with an apparent KD of 2.9 µM. Cocrystallization screens of DsbA and the VKOR
heptapeptide were set up and crystals were obtained. The cloning and protein overexpression of two different
constructs of DsbA-VKOR fusion proteins was performed. I was able to successfully obtain crystals for
DsbA alone and for the cocrystallization of DsbA with the VKOR heptapeptide. In addition, we believe that
the DsbA-VKOR fusion protein was successfully overexpressed in a condition that resembles the
overexpression conditions of full-length VKOR in Synechococcus sp.