Copper ion is essential yet toxic for all living organisms. Because of this dual nature, cells must posses a dynamic homeostasis to maintain a proper cellular level of copper ion: not too low to cause deficiency and not too high to cause toxicity. What is the molecular mechanism of dynamic copper ion homeostasis? This is still a fundamental question to be addressed. Therefore, it is absolutely critical to understand copper ion homeostatic mechanisms. The goal of this project is, using yeast as a model system, to study the dynamic regulation of copper ion homeostasis. Yeast cells carry out similar biochemical reactions to those required in humans, and copper ion homeostatic mechanisms are largely conserved among yeast, human and other divergent species. In yeast, copper ion uptake and transport under physiological conditions is regulated by a putative copper ion-sensing protein, Mac 1p. Recent studies have shown that Mac lp also responds to toxic levels of copper ions through an uncharacterized mechanism of regulated protein degradation. Mac lp degradation is a new mechanism in copper ion homeostasis. The differential functions of Mac lp under physiological and toxic copper ion conditions reflect the dynamic biological nature of copper ions. Therefore, understanding Mac lp functions will be instrumental in determining molecular mechanism of dynamic copper ion homeostasis. This project, using a combination of molecular biological, chemical and biochemical methods, will to determine the precise molecular mechanisms of Mac lp functions. These approaches will be applied to achieve two specific aims: (1) to further characterize how Mac lp responds differentially to physiological and toxic levels of copper ions, (2) to elucidate the biochemical mechanisms of Mac 1p sensing and differentiating physiological and toxic levels of copper ions. The outcomes of this research will make fundamental contributions to understanding of the molecular mechanism of dynamic copper ion homeostasis. The results will also provide critical insights into the fields of metal ions in biology and regulated protein degradation.
