Magnesium (Mg2+) is required for the catalytic activity of numerous metalloenzymes within a variety of subcellular organelles. Membrane magnesium transporter 1 (MMGT1) mediates the uptake of Mg2+ across the Golgi membrane. The human MMGT1 function is inferred from mouse experiments using the orthologous Mmgt1 and 2 (Goytain & Quamme 2008). MMGT1 is also found on the ER membrane as a component of the ER membrane protein complex (EMC) which functions to degrade incorrectly folded or assembled proteins by a ubiquitin- and proteasome-dependent process known as ER-associated degradation (ERAD). MMGT1 is not implicated in this function of protein quality control (Christianson et al. 2011).