This entry represents a family of membrane magnesium transporters (MMgT) []. The proteins, MMgT1 (also known as ER membrane protein complex subunit 5) and MMgT2, are localised to the Golgi complex and post-Golgi vesicles, including the early endosomes, suggesting that they may provide regulated pathways for Mg2+ transport in the Golgi and post-Golgi organelles of epithelium-derived cells []. MMgT1 is part of the endoplasmic reticulum membrane protein complex (EMC) that enables the energy-independent insertion into endoplasmic reticulum membranes of newly synthesized membrane proteins and it is also involved in the cotranslational insertion of multi-pass membrane proteins in which stop-transfer membrane-anchor sequences become ER membrane spanning helices [, , , , ]. MMgT1 is also required for the post-translational insertion of tail-anchored proteins in endoplasmic reticulum membranes [, ]and mediates the proper cotranslational insertion of N-terminal transmembrane domains in an N-exo topology thus, controlling the topology of multi-pass membrane proteins like the G protein-coupled receptors [].
