Magnesium transporters E (MgtE) are a family of transmembrane eubacterial MgtE

magnesium transporter Magnesium transporters are proteins that transport magnesium across the cell membrane. All forms of life require magnesium, yet the molecular mechanisms of Mg2+ uptake from the environment and the distribution of this vital element within the organi ...

s. Related regions are found also in

archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...

l and eukaryotic proteins. They have sizes that vary considerably from 311 residues for the ''Methanococcus thermoautotrophicum'' protein, 463 residues for a '' Synechocystis'' homologue, and 513 residues for the human homologue, SLC41A1. These proteins are capable of transporting Mg²⁺ and Co²⁺ but not Ni²⁺. Multiple alignments contain two

highly conserved In evolutionary biology, conserved sequences are identical or similar sequences in nucleic acids ( DNA and RNA) or proteins across species ( orthologous sequences), or within a genome ( paralogous sequences), or between donor and receptor taxa ( ...

aspartate Aspartic acid (symbol Asp or D; the ionic form is known as aspartate), is an α-amino acid that is used in the biosynthesis of proteins. Like all other amino acids, it contains an amino group and a carboxylic acid. Its α-amino group is in the pro ...

s that may be involved in

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

binding. Human transporters from this family are

SLC41A1 SLC41A1 is a protein that in humans is encoded by the gene SLC41A1. It is homologous to the prokaryotic Mg++ transfer protein MgtE Mutations in this gene have been associated to Nephronophthisis Nephronophthisis is a genetic disorder of the kid ...

, SLC41A2 and SLC41A3.

Structure and Mechanism

The ''

Bacillus firmus ''Bacillus firmus'' is a species of bacteria within the genus ''Bacillus''. Some strains of this species are very alkaline-tolerant and may grow in environments with pH as high as 11. This species has been recently transferred into the genus '' ...

'' 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 resembles

l inositol monophosphate dehydrogenases. Kehres and Maguire suggest that the MgtE proteins are secondary carriers with inwardly directed polarity. 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. This produces a mechanism for the maintenance of homeostasis conditions. 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 the electrochemical potential of Mg²⁺. 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.

Transport Reaction

The transport reaction catalyzed by MgtE proteins is: :Mg²⁺ (or Co²⁺) (out) → Mg²⁺ (or Co²⁺) (in)

References

{{CCBYSASource, sourcepath= http://tcdb.org/search/result.php?tc=1.A.26, sourcearticle= 1.A.26 The Mg2+ Transporter-E (MgtE) Family , revision=699838558 Protein families Solute carrier family