| MgtE | |||||||||
|---|---|---|---|---|---|---|---|---|---|
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| Identifiers | |||||||||
| Symbol | MgtE | ||||||||
| Pfam | PF01769 | ||||||||
| InterPro | IPR006667 | ||||||||
| TCDB | 1.A.26 | ||||||||
| OPM superfamily | 180 | ||||||||
| OPM protein | 2yvx | ||||||||
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Magnesium transporters E (MgtE) are a family of transmembrane eubacterial MgtEmagnesium transporters. Related regions are found also inarchaeal andeukaryoticproteins. They have sizes that vary considerably from 311 residues for theMethanococcus thermoautotrophicum protein, 463 residues for aSynechocystis homologue, and 513 residues for the human homologue, SLC41A1. These proteins are capable of transporting Mg2+ and Co2+ but not Ni2+. Multiplealignments contain twohighly conservedaspartates that may be involved incationbinding.
Human transporters from this family areSLC41A1,SLC41A2 andSLC41A3.
TheBacillus firmus transporter and several homologues examined have strongly charged, hydrophilic N-terminal domains (cytoplasmic) followed by a hydrophobic C-terminal domain with 5 putative transmembrane α-helical spanners. A central 100 residues resemblesarchaeal inositol monophosphate dehydrogenases.[2]
Kehres and Maguire suggest that the MgtE proteins are secondary carriers with inwardly directed polarity.[2] Hattori et al. have considered MgtE to function by a channel mechanism, providing evidence that the MgtE cytosolic domain acts as a Mg2+ sensor to regulate gating of the pore in response to the intracellular Mg2+ concentration.[1] This produces a mechanism for the maintenance of homeostasis conditions.[1] The cytosolic domain of MgtE undergoes a Mg2+-dependent structural change, which may gate the ion-conducting pore passing through the transmembrane domain.
Maruyama et al. showed that MgtE exhibits the channel-like electrophysiological properties, i.e., Mg2+ transport occurs in accordance to theelectrochemical potential of Mg2+.[3] The Mg2+-permeation pathway opens in response to a decrease of the intracellular Mg2+ concentration, while it is completely closed at the intracellular Mg2+ concentration of 10 mM. The crystal structures of the MgtE dimer reveal that the Mg2+-sensing cytoplasmic region consists of the N and CBS domains. The Mg2+-bound state adopts a compact, globular conformation, which is stabilized by the coordination of a number of Mg2+ ions between these domains. On the other hand, in the Mg2+-unbound state, these domains are far apart, and fixed by the crystal packing.
The transport reaction catalyzed by MgtE proteins is:
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