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 Mg
2+ and Co
2+ but not Ni
2+. 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
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 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 Mg
2+ sensor to regulate gating of the pore in response to the intracellular Mg
2+ concentration.
This produces a mechanism for the maintenance of homeostasis conditions.
The cytosolic domain of MgtE undergoes a Mg
2+-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., Mg
2+ transport occurs in accordance to the
electrochemical potential of Mg
2+.
The Mg
2+-permeation pathway opens in response to a decrease of the intracellular Mg
2+ concentration, while it is completely closed at the intracellular Mg
2+ concentration of 10 mM. The crystal structures of the MgtE dimer reveal that the Mg
2+-sensing cytoplasmic region consists of the N and CBS domains. The Mg
2+-bound state adopts a compact, globular conformation, which is stabilized by the coordination of a number of Mg
2+ ions between these domains. On the other hand, in the Mg
2+-unbound state, these domains are far apart, and fixed by the crystal packing.
Transport Reaction
The transport reaction catalyzed by MgtE proteins is:
:Mg
2+ (or Co
2+) (out) → Mg
2+ (or Co
2+) (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