Contribution of the Mnr2 Protein to Magnesium Homeostasis in Saccharomyces cerevisiae

Magnesium is an essential metal nutrient with diverse roles in biology. To maintain the optimal function of key biological processes, intracellular Mg2+ concentration is tightly regulated. Despite the importance of this process however, relatively little is known about mechanisms of Mg2+ homeostasis in eukaryotic cells. An understanding of homeostasis starts with defining the function of key transport proteins that allow the passage of Mg2+ ions across the membranes. Yeast geneticists have identified four proteins from Bakers\u27 yeast (Saccharomyces cerevisiae) involved in regulating the accumulation of Mg2+ within the cell (Alr1 and Alr2) and within the mitochondrial compartment (Mrs2 and Lpe10). These proteins all belong to a superfamily of Mg2+ channels that also include members from prokaryotic and higher eukaryotic organisms. A fifth yeast protein (Mnr2) also belongs to this family, but its function has not been defined. This work describes the results of experiments performed to identify the unique role of Mnr2 in the cell, and its relationship to other related proteins. These observations also define a novel process (intracellular Mg2+ storage) that significantly enhances tolerance to environmental variation