InterPro domain: IPR018937

This entry represents a family of membrane magnesium transporters (MMgT) [ 1 ]. 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 [ 2 ]. 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 [ 2 , 3 , 4 , 5 , 6 ]. MMgT1 is also required for the post-translational insertion of tail-anchored proteins in endoplasmic reticulum membranes [ 7 , 7 ] 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 [ 7 ].

1. Identification and characterization of a novel family of membrane magnesium transporters, MMgT1 and MMgT2. Am. J. Physiol., Cell Physiol. 294, C495-502
2. EMC Is Required to Initiate Accurate Membrane Protein Topogenesis. Cell 175, 1507-1519.e16
3. The ER membrane protein complex interacts cotranslationally to enable biogenesis of multipass membrane proteins. Elife 7, 470-473
4. The ER membrane protein complex is a transmembrane domain insertase. Science 359, 433-436
5. The architecture of EMC reveals a path for membrane protein insertion. Elife 9
6. Structural basis for membrane insertion by the human ER membrane protein complex. Science 369