Krishan Jethwa

Gene regulation of the cadmium-binding protein MBII

Biology or Chemistry, Dr. Dahlseid


About My Research:

MPII is a small cadmium-binding protein that is involved in the cellular detoxification of cadmium. It was previously observed that MPII protein levels were higher in cadmium treated cells, while the levels of the molecule responsible for encoding for the MPII protein, mRNA, remained the same (Demuynck et al. 2004). In response to this finding, our goal became to test the potential for regulation of MPII. We have hypothesized possible mechanisms for its gene regulation. In the presence of higher cadmium levels, the equilibrium would shift such that there would be a higher concentration of an MPII/cadmium complex. This complex could then bind its own mRNA to enhance protein synthesis or loose the ability to bind its own mRNA thus reducing repression of protein synthesis.  Both of these mechanisms would increase MPII protein levels while leaving the MPII mRNA levels unchanged. Alternatively, it is also possible that the MPII/cadmium complex remains intact longer than free MPII protein. In order to test whether this increase in protein levels is due to regulation or stability, MPII will be cloned into Baker’s yeast. Cloning into Baker’s yeast would allow us to experimentally test for what type of mechanism is occurring.

Professional Abstract:

Glutathione plays an important biological role in detoxication in nearly all eukaryotes. Recently, it has been implicated in chemotherapeutic resistance due to its high abundance in many cancer cells and its ability to slow or block chemotherapeutic effects. By inhibiting glutathione synthesis, cancer cells may become more susceptible to some therapeutic techniques. The enzyme, γ-glutamylcysteine synthetase (γ-GCS) catalyzes the first step in the synthesis of glutathione. In the present study, UV/Vis spectroscopy was used to identify substrate analogs that alter the activity of γ-GCS, while fluorescence spectroscopy was used to probe the effect of these analogs on the binding of natural substrates. These studies suggest that the enzyme active site contains two distinct binding sites that may be filled with a cysteine-like molecule. To further investigate the metal-binding sites of γ-GCS, preliminary titration studies with cobalt were performed for future study of the enzyme using NMR.