The Human Mitochondrial Mrs2 Protein Functionally Substitutes for Its Yeast Homologue, A Candidate Magnesium Transporter

doi:10.1006/geno.2000.6407

Genomics

Volume 72, Issue 2, 1 March 2001, Pages 158-168

https://doi.org/10.1006/geno.2000.6407 Get rights and content

Abstract

We report here on the human MRS2 gene that encodes a protein, hsaMrs2p, the first molecularly characterized candidate for a magnesium transporter in metazoa. The protein, like the yeast mitochondrial Mrs2 and Lpe10 proteins, contains two predicted transmembrane domains in its carboxyl-terminus, the first of which terminates with the conserved motif F/Y-G-M-N. These are typical features of the CorA family of magnesium transporters. Expression of hsaMrs2p in mrs2-1 knock-out mutant yeast partly restores mitochondrial magnesium concentrations that are significantly reduced in this mutant. It also alleviates other defects of this mutant, which may be secondary to the reduction in magnesium concentrations. These findings suggest that hsaMrs2p and yMrs2p are functional homologues. Like its yeast homologues, hsaMrs2p has been localized in mitochondria. The hsaMRS2 gene is located on chromosome 6 (6p22.1–p22.3) and is composed of 11 exons. A low level of the transcript is detected in various mouse tissues.

References (31)

D.M. Bui et al.
The bacterial magnesium transporter CorA can functionally substitute for its putative homologue Mrs2p in the yeast inner mitochondrial membrane
J. Biol. Chem.
(1999)
C. Cefaratti et al.
Differential localization and operation of distinct Mg²⁺ transporters in apical and basolateral sides of rat liver plasma membrane
J. Biol. Chem.
(2000)
S.H. Cross et al.
CpG islands and genes
Curr. Opin. Genet. Dev.
(1995)
O. Emanuelsson et al.
Predicting subcellular localization of proteins based on their N-terminal amino acid sequence
J. Mol. Biol.
(2000)
T.S. Heard et al.
A regional net charge and structural compensation model to explain how negatively charged amino acids can be accepted within a mitochondrial leader sequence
J. Biol. Chem.
(1998)
D.W. Jung et al.
On the relationship between matrix free Mg²⁺ concentration and total Mg²⁺ in heart mitochondria
Biochim. Biophys. Acta
(1997)
M. Kozak
Structural features in eukaryotic mRNAs that modulate the initiation of translation
J. Biol. Chem.
(1991)
C.W. MacDiarmid et al.
Overexpression of the Saccharomyces cerevisiae magnesium transport system confers resistance to aluminum ion
J. Biol. Chem.
(1998)
A. Romani et al.
Regulation of cell magnesium
Arch. Biochem. Biophys.
(1992)
U. Schmidt et al.
Mutant alleles of the MRS2 gene of yeast nuclear DNA suppress mutations in the catalytic core of a mitochondrial group II intron
J. Mol. Biol.
(1998)

M.A. Szegedy et al.

The CorA Mg²⁺ transport protein of Salmonella typhimurium. Mutagenesis of conserved residues in the second membrane domain

J. Biol. Chem.

(1999)

I.A. Trounce et al.

Assessment of mitochondrial oxidative phosphorylation in patient muscle biopsies, lymphoblasts, and transmitochondrial cell lines

Methods Enzymol.

(1996)

T. Vernet et al.

A family of yeast expression vectors containing the phage f1 intergenic region

Gene

(1987)

G. Wiesenberger et al.

The nuclear gene MRS2 is essential for the excision of group II introns from yeast mitochondrial transcripts in vivo

J. Biol. Chem.

(1992)

S.F. Altschul et al.

Gapped BLAST and PSI-BLAST: A new generation of protein database search programs

Nucleic Acids Res.

(1997)

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Citation Excerpt :
Similar to the SLC41 family, the CNNM family transporters have also been reported to localize at the basolateral membrane with Na+-driven Mg2+ efflux activity.13,17 Finally, Mrs2 is a mitochondrial inner membrane protein that mediates essential Mg2+ transport for mitochondrial metabolic functions.18–19 Structural information is required to understand the Mg2+ transport mechanisms associated with these channel and transporter proteins (Figure 1(B)-1(E)), but only a few structures of prokaryotic origin, such as the crystal structures of CorA (bacterial homologue of Mrs2)20–24 and MgtE (bacterial homologue of SLC41),25–26 were available until recently.
Magnesium ions (Mg²⁺) are the most abundant divalent cations in living organisms and are essential for various physiological processes, including ATP utilization and the catalytic activity of numerous enzymes. Therefore, the homeostatic mechanisms associated with cellular Mg²⁺ are crucial for both eukaryotic and prokaryotic organisms and are thus strictly controlled by Mg²⁺ channels and transporters. Technological advances in structural biology, such as the expression screening of membrane proteins, in meso phase crystallization, and recent cryo-EM techniques, have enabled the structure determination of numerous Mg²⁺ channels and transporters. In this review article, we provide an overview of the families of Mg²⁺ channels and transporters (MgtE/SLC41, TRPM6/7, CorA/Mrs2, CorC/CNNM), and discuss the structural biology prospects based on the known structures of MgtE, TRPM7, CorA and CorC.
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Professor Bruce Ames demonstrated that nutritional recommendations should be adjusted in order to ‘tune-up’ metabolism and reduce mitochondria decay, a hallmark of aging and many disease processes. A major subset of tunable nutrients are the minerals, which despite being integral to every aspect of metabolism are often deficient in the typical Western diet. Mitochondria are particularly rich in minerals, where they function as essential cofactors for mitochondrial physiology and overall cellular health. Yet substantial knowledge gaps remain in our understanding of the form and function of these minerals needed for metabolic harmony. Some of the minerals have known activities in the mitochondria but with incomplete regulatory detail, whereas other minerals have no established mitochondrial function at all. A comprehensive metallome of the mitochondria is needed to fully understand the patterns and relationships of minerals within metabolic processes and cellular development. This brief overview serves to highlight the current progress towards understanding mineral homeostasis in the mitochondria and to encourage more research activity in key areas. Future work may likely reveal that adjusting the amounts of specific nutritional minerals has longevity benefits for human health.
Mitochondrial osmoregulation in evolution, cation transport and metabolism
2021, Biochimica et Biophysica Acta - Bioenergetics
Citation Excerpt :
As with other cations, mitochondrial Mg2+ levels are governed against the electrochemical equilibrium by inward and outward fluxes. The inward fluxes are mediated in dependence of the membrane potential by MRS2, the first molecularly identified mitochondrial cation transporter [121,122]. Mg2+ efflux has been proposed to work in exchange for ATP, H+ or Na+, and the Mg2+/Na+ carrier SLC41A3 is the only mitochondrial Mg2+ efflux system identified to date [123] (Fig. 1A).
This review provides a retrospective on the role of osmotic regulation in the process of eukaryogenesis. Specifically, it focuses on the adjustments which must have been made by the original colonizing α-proteobacteria that led to the evolution of modern mitochondria. We focus on the cations that are fundamentally involved in volume determination and cellular metabolism and define the transporter landscape in relation to these ions in mitochondria as we know today. We provide analysis on how the cations interplay and together maintain osmotic balance that allows for effective ATP synthesis in the organelle.
A novel mitochondrial carrier protein Mme1 acts as a yeast mitochondrial magnesium exporter
2015, Biochimica et Biophysica Acta - Molecular Cell Research
Citation Excerpt :
The decrease in mitochondrial Mg2 + content of the mrs2Δ mutant can be rescued by the expression of bacterial Mg2 + transporter CorA fused to a mitochondrial N-terminal leader sequence of MRS2 [13]. The functional complementation was also observed with the orthologue of Mrs2 in humans [14]. Yeast Lpe10 also localizes at the mitochondrial inner membrane and shares 32% of its sequence identity and a conserved GMN motif with Mrs2 [15].
The homeostasis of magnesium (Mg^2 +), an abundant divalent cation indispensable for many biological processes including mitochondrial functions, is underexplored. Previously, two mitochondrial Mg^2 + importers, Mrs2 and Lpe10, were characterized for mitochondrial Mg^2 + uptake. We now show that mitochondrial Mg^2 + homeostasis is accurately controlled through the combined effects of previously known importers and a novel exporter, Mme1 (mitochondrial magnesium exporter 1). Mme1 belongs to the mitochondrial carrier family and was isolated for its mutation that is able to suppress the mrs2Δ respiration defect. Deletion of MME1 significantly increased steady-state mitochondrial Mg^2 + concentration, while overexpression decreased it. Measurements of Mg^2 + exit from proteoliposomes reconstituted with purified Mme1 provided definite evidence for Mme1 as an Mg^2 + exporter. Our studies identified, for the first time, a mitochondrial Mg^2 + exporter that works together with mitochondrial importers to ensure the precise control of mitochondrial Mg^2 + homeostasis.
The structure and regulation of magnesium selective ion channels
2013, Biochimica et Biophysica Acta - Biomembranes
The magnesium ion (Mg^2 +) is the most abundant divalent cation within cells. In man, Mg^2 +-deficiency is associated with diseases affecting the heart, muscle, bone, immune, and nervous systems. Despite its impact on human health, little is known about the molecular mechanisms that regulate magnesium transport and storage. Complete structural information on eukaryotic Mg^2 +-transport proteins is currently lacking due to associated technical challenges. The prokaryotic MgtE and CorA magnesium transport systems have recently succumbed to structure determination by X-ray crystallography, providing first views of these ubiquitous and essential Mg^2 +-channels. MgtE and CorA are unique among known membrane protein structures, each revealing a novel protein fold containing distinct arrangements of ten transmembrane-spanning α-helices. Structural and functional analyses have established that Mg^2 +-selectivity in MgtE and CorA occurs through distinct mechanisms. Conserved acidic side-chains appear to form the selectivity filter in MgtE, whereas conserved asparagines coordinate hydrated Mg^2 +-ions within the selectivity filter of CorA. Common structural themes have also emerged whereby MgtE and CorA sense and respond to physiologically relevant, intracellular Mg^2 +-levels through dedicated regulatory domains. Within these domains, multiple primary and secondary Mg^2 +-binding sites serve to staple these ion channels into their respective closed conformations, implying that Mg^2 +-transport is well guarded and very tightly regulated. The MgtE and CorA proteins represent valuable structural templates to better understand the related eukaryotic SLC41 and Mrs2–Alr1 magnesium channels. Herein, we review the structure, function and regulation of MgtE and CorA and consider these unique proteins within the expanding universe of ion channel and transporter structural biology.
Membrane protein interactions between different Arabidopsis thaliana MRS2-type magnesium transporters are highly permissive
2013, Biochimica et Biophysica Acta - Biomembranes
Citation Excerpt :
The gene and protein designations in yeast and bacteria reflect the initially observed phenotypes (e.g. CorA: cobalt resistance, MRS2: mitochondrial RNA splicing, ALR: aluminium resistance or MNR: manganese resistance) when the respective genes encoding 2-TM-GMN proteins are defect or over-expressed [3–7]. Their key function, however, is obviously the transport of Mg2 + across biological membranes, as conclusively demonstrated by their ability to complement defects of magnesium transport in respective mutants of the diverse genetic systems even across wide phylogenetic distances [8–14]. Moreover, a high-conductance (~ 155 pS) Mg2 + flux was demonstrated directly in single-channel patch clamping experiments of MRS2 in giant lipid vesicles [15,16].
Membrane proteins of the Arabidopsis thaliana MRS2 (MGT) family have been characterised as magnesium transporters. Like their bacterial CorA homologues, the plant MRS2 proteins are characterised by an invariable GMN tripeptide motif terminating the first of two closely spaced transmembrane domains at the carboxy-termini. The functional Mg^2 + transport channel is assembled as a pentamer in the case of CorA. However, in contrast to the single CorA genes of bacteria, plant genomes encode up to 10 highly divergent MRS2 proteins. To elucidate structure–function relationships and the possibility of plant MRS2 hetero-pentamer formation, we performed protein–protein interaction studies in the yeast mating-based split-ubiquitin system (mbSUS) and concomitant protein modelling using I-TASSER. Despite very restricted sequence similarities and variable polypeptide insertions all AtMRS2 proteins feature the key structural elements determined for the CorA crystal structure. The mbSUS setup conclusively demonstrates protein–protein interactions of any given AtMRS2 protein not only with itself but also highly permissive interactions to varying degrees among all AtMRS2 proteins. AtMRS2-3 seems particularly prone to non-selective, strong interactions with the other homologues. Deletion constructs show that six amino acids may be deleted from the carboxy-terminus and 27 (but not 41) from the amino-terminus of AtMRS2-7 without impairment of homologous or heterologous protein interactions. Despite significant diversification, the plant MRS2 proteins have obviously retained an ancient CorA/MRS2 core structure and the capacity for protein–protein interactions. Plant magnesium homeostasis may be influenced by hetero-oligomer channel formation where different plant MRS2 proteins meet in the same membrane naturally or in transgenic approaches.

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^☆: Sequence data from this article have been deposited with the EMBL/GenBank Data Libraries under Accession Nos. AF293076–AF293078.

¹: To whom correspondence should be addressed. Telephone: +43 1 4277-54604. Fax: +43 1 4277-9546. E-mail: [email protected].

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Regular ArticleThe Human Mitochondrial Mrs2 Protein Functionally Substitutes for Its Yeast Homologue, A Candidate Magnesium Transporter☆

Abstract

J. Biol. Chem.

J. Biol. Chem.

Curr. Opin. Genet. Dev.

J. Mol. Biol.

J. Biol. Chem.

Biochim. Biophys. Acta

J. Biol. Chem.

J. Biol. Chem.

Arch. Biochem. Biophys.

J. Mol. Biol.

J. Biol. Chem.

Methods Enzymol.

Gene

J. Biol. Chem.

Gapped BLAST and PSI-BLAST: A new generation of protein database search programs

Nucleic Acids Res.

Regular Article
The Human Mitochondrial Mrs2 Protein Functionally Substitutes for Its Yeast Homologue, A Candidate Magnesium Transporter☆