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Michael E. Maguire - One of the best experts on this subject based on the ideXlab platform.
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the cora mg2 transporter is a homotetramer
Journal of Bacteriology, 2004Co-Authors: Mary Ann Warren, Lisa M. Kucharski, Alexander A. Veenstra, Liang Shi, Paul F. Grulich, Michael E. MaguireAbstract:Salmonella enterica serovar Typhimurium has three transport systems mediating influx of Mg2+: CorA, MgtA, and MgtB (6, 7, 22, 24). The CorA system is encoded by the corA gene that constitutively expresses a 37-kDa integral membrane protein (19).
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cation hexaammines are selective and potent inhibitors of the cora magnesium transport system
Journal of Biological Chemistry, 2000Co-Authors: Lisa M. Kucharski, Wil J Lubbe, Michael E. MaguireAbstract:Abstract Cation hexaammines and related compounds are chemically stable analogs of the hydrated form of cations, particularly Mg2+. We tested the ability of several of these compounds to inhibit transport by the CorA or MgtB Mg2+transport systems or the PhoQ receptor kinase for Mg2+ inSalmonella typhimurium. Cobalt(III)-, ruthenium(II)-, and ruthenium(III)-hexaammines were potent inhibitors of CorA-mediated influx. Cobalt(III)- and ruthenium(III)chloropentaammines were slightly less potent inhibitors of CorA. The compounds inhibited uptake by the bacterial S. typhimurium CorA and by the archaealMethanococcus jannaschii CorA, which bear only 12% identity in the extracellular periplasmic domain. Cation hexaammines also inhibited growth of S. typhimurium strains dependent on CorA for Mg2+ uptake but not of isogenic strains carrying a second Mg2+ uptake system. In contrast, hexacyano-cobaltate(III) and ruthenate(II)- and nickel(II)hexaammine had little effect on uptake. The inhibition by the cation hexaammines was selective for CorA because none of the compounds had any effect on transport by the MgtB P-type ATPase Mg2+ transporter or the PhoQ Mg2+ receptor kinase. These results demonstrate that cation hexaammines are potent and highly selective inhibitors of the CorA Mg2+ transport system and further indicate that the initial interaction of the CorA transporter is with a fully hydrated Mg2+ cation.
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the cora mg2 transport protein of salmonella typhimurium mutagenesis of conserved residues in the second membrane domain
Journal of Biological Chemistry, 1999Co-Authors: Mary Ann Szegedy, Michael E. MaguireAbstract:Abstract Salmonella typhimurium CorA is the archetypal member of the largest family of Mg2+transporters of the Bacteria and Archaea. It contains three transmembrane segments. There are no conserved charged residues within these segments indicating electrostatic interactions are not used in Mg2+ transport through CorA. Previous mutagenesis studies of CorA revealed a single face of the third transmembrane segment that is important for Mg2+ transport. In this study, we mutated hydroxyl-bearing and other conserved residues in the second transmembrane segment to identify residues involved in transport. Residues Ser260, Thr270, and Ser274appear to be important for transport and are oriented such that they would also line a face of an α-helix. In addition, the sequence276YGMNF280, found in virtually all CorA homologues, is critical for CorA function because even conservative mutations are not tolerated at these residues. Finally, mutations of residues in the second transmembrane segment, unlike those in the third transmembrane segment, revealed cooperative behavior for the influx of Mg2+. We conclude that the second transmembrane segment forms a major part of the Mg2+ pore with the third transmembrane segment of CorA.
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sequence and topology of the cora magnesium transport systems of salmonella typhimurium and escherichia coli identification of a new class of transport protein
Journal of Biological Chemistry, 1993Co-Authors: Ronald L Smith, J L Banks, M D Snavely, Michael E. MaguireAbstract:The CorA Mg2+ transport systems of Salmonella typhimurium and Escherichia coli mediate both influx and efflux of Mg2+. The product of the CorA locus is sufficient for mediation of Mg2+ influx while product(s) of the unlinked CorBCD loci allow CorA to mediate efflux in addition to influx. The nucleotide sequences of the S. typhimurium and E. coli CorA loci have been determined. The locus in each species consists of a single gene expressing a protein with gel molecular masses of 42 kDa (S. typhimurium) and 39 kDa (E. coli). The predicted amino acid sequences of these proteins are each 316 amino acids in length, are 98% identical, and lack homology to any known protein. Although CorA is an integral membrane protein by biochemical criteria, its predicted amino acid sequence contains 28% charged amino acid. Membrane localization of CorA was shown to be dependent on the Sec pathway in E. coli. Hydropathy analysis predicts two C-terminal hydrophobic sequences of sufficient length to span the membrane bilayer. The membrane topology of CorA was determined by constructing deletion derivatives of CorA and genetically fusing them to BlaM or LacZ cassettes. The enzymatic activities of these hybrid proteins indicate that the N-terminal 235 amino acid residues of the CorA protein are located within the periplasmic space, comprising a single periplasmic domain. The C-terminal region of CorA is composed of three membrane-spanning segments rather than the two suggested by hydropathy plots, thus depositing the C terminus within the cytoplasm. This topology suggests that CorA functions as an oligomer since three membrane loops are most likely insufficient for any sort of membrane pore or channel. Its lack of homology to known proteins and its topology indicate that the CorA Mg2+ transporter represents a new class of membrane transport system.
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magnesium transport in salmonella typhimurium the influence of new mutations conferring co2 resistance on the cora mg2 transport system
Molecular Microbiology, 1991Co-Authors: M M Gibson, D A Bagga, C G Miller, Michael E. MaguireAbstract:Summary The CorA Mg2+ transport system of Salmonella typhimurium mediates both influx and efflux of Mg2+. Mutations at the corA locus (83.5min) confer resistance to Co2+. Using transposon mutagenesis, three additional Co2+ resistance loci (corB, corC, and corD) were found and mapped to 55, 15, and 3min, respectively, on the S. typhimurium chromosome. No mutations corresponding to the reported corB locus at 95min in Escherichia coli were obtained. The corB, corC, and corD mutations confer levels of Co2+ resistance intermediate between those of the wild-type and corA mutations. Isogenic strains were constructed containing combinations of transposon insertion mutations in each of the three Co2+ resistance loci to assess their influence on the CorA Mg2+ transport system. The Vmax and Km values for 28Mg2+ or for 57Co2+ and 63Ni2+ influx, analogues of Mg2+ transported by the CorA system, were changed less than twofold compared with the wild-type values, regardless of the mutation(s) present. However, while efflux of 28Mg2+ through the CorA system was decreased threefold in strains carrying one or two mutant alleles among corB, corC, or corD, efflux was completely abolished in either a corA or a corBCD strain. Thus, although the corA gene product is necessary and sufficent to mediate Mg2+ influx, Mg2+ efflux requires the presence of a wild-type allele of at least one of the corB, corC or corD loci.
Said Eshaghi - One of the best experts on this subject based on the ideXlab platform.
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exploring the structure and function of thermotoga maritima cora reveals the mechanism of gating and ion selectivity in co2 mg2 transport
Biochemical Journal, 2013Co-Authors: Nurhuda Nordin, Albert Guskov, Terri Phua, Newsha Sahaf, Yu Xia, Hojjat Eshaghi, Said EshaghiAbstract:The CorA family of divalent cation transporters utilizes Mg2+ and Co2+ as primary substrates. The molecular mechanism of its function, including ion selectivity and gating, has not been fully characterized. Recently we reported a new structure of a CorA homologue from Methanocaldococcus jannaschii, which provided novel structural details that offered the conception of a unique gating mechanism involving conversion of an open hydrophilic gate into a closed hydrophobic one. In the present study we report functional evidence for this novel gating mechanism in the Thermotoga maritima CorA together with an improved crystal structure of this CorA to 2.7 A (1 A=0.1 nm) resolution. The latter reveals the organization of the selectivity filter to be similar to that of M. jannaschii CorA and also the previously unknown organization of the second signature motif of the CorA family. The proposed gating is achieved by a helical rotation upon the binding of a metal ion substrate to the regulatory binding sites. Additionally, our data suggest that the preference of this CorA for Co2+ over Mg2+ is controlled by the presence of threonine side chains in the channel. Finally, the roles of the intracellular metal-binding sites have been assigned to increased thermostability and regulation of the gating. These mechanisms most likely apply to the entire CorA family as they are regulated by the highly conserved amino acids.
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co2 selectivity of thermotoga maritima cora and its inability to regulate mg2 homeostasis present a new class of cora proteins
Journal of Biological Chemistry, 2011Co-Authors: Yu Xia, Newsha Sahaf, Annakarin Lundback, Gustav Nordlund, Peter Brzezinski, Said EshaghiAbstract:CorA is a family of divalent cation transporters ubiquitously present in bacteria and archaea. Although CorA can transport both Mg(2+) and Co(2+) almost equally well, its main role has been suggest ...
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co2 selectivity of thermotoga maritima cora and its inability to regulate mg2 homeostasis present a new class of cora proteins
Journal of Biological Chemistry, 2011Co-Authors: Yu Xia, Newsha Sahaf, Annakarin Lundback, Gustav Nordlund, Peter Brzezinski, Said EshaghiAbstract:CorA is a family of divalent cation transporters ubiquitously present in bacteria and archaea. Although CorA can transport both Mg2+ and Co2+ almost equally well, its main role has been suggested to be that of primary Mg2+ transporter of prokaryotes and hence the regulator of Mg2+ homeostasis. The reason is that the affinity of CorA for Co2+ is relatively low and thus considered non-physiological. Here, we show that Thermotoga maritima CorA (TmCorA) is incapable of regulating the Mg2+ homeostasis and therefore cannot be the primary Mg2+ transporter of T. maritima. Further, our in vivo experiments confirm that TmCorA is a highly selective Co2+ transporter, as it selects Co2+ over Mg2+ at >100 times lower concentrations. In addition, we present data that show TmCorA to be extremely thermostable in the presence of Co2+. Mg2+ could not stabilize the protein to the same extent, even at high concentrations. We also show that addition of Co2+, but not Mg2+, specifically induces structural changes to the protein. Altogether, these data show that TmCorA has the role of being the transporter of Co2+ but not Mg2+. The physiological relevance and requirements of Co2+ in T. maritima is discussed and highlighted. We suggest that CorA may have different roles in different organisms. Such functional diversity is presumably a reflection of minor, but important structural differences within the CorA family that regulate the gating, substrate selection, and transport.
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crystal structure of a divalent metal ion transporter cora at 2 9 angstrom resolution
Science, 2006Co-Authors: Said Eshaghi, Daniel Martinez Molina, Scott A Lesley, Andreas Kohl, Damian Niegowski, Par NordlundAbstract:CorA family members are ubiquitously distributed transporters of divalent metal cations and are considered to be the primary Mg2+ transporter of Bacteria and Archaea. We have determined a 2.9 angstrom resolution structure of CorA from Thermotoga maritima that reveals a pentameric cone–shaped protein. Two potential regulatory metal binding sites are found in the N-terminal domain that bind both Mg2+ and Co2+. The structure of CorA supports an efflux system involving dehydration and rehydration of divalent metal ions potentially mediated by a ring of conserved aspartate residues at the cytoplasmic entrance and a carbonyl funnel at the periplasmic side of the pore.
Yu Xia - One of the best experts on this subject based on the ideXlab platform.
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exploring the structure and function of thermotoga maritima cora reveals the mechanism of gating and ion selectivity in co2 mg2 transport
Biochemical Journal, 2013Co-Authors: Nurhuda Nordin, Albert Guskov, Terri Phua, Newsha Sahaf, Yu Xia, Hojjat Eshaghi, Said EshaghiAbstract:The CorA family of divalent cation transporters utilizes Mg2+ and Co2+ as primary substrates. The molecular mechanism of its function, including ion selectivity and gating, has not been fully characterized. Recently we reported a new structure of a CorA homologue from Methanocaldococcus jannaschii, which provided novel structural details that offered the conception of a unique gating mechanism involving conversion of an open hydrophilic gate into a closed hydrophobic one. In the present study we report functional evidence for this novel gating mechanism in the Thermotoga maritima CorA together with an improved crystal structure of this CorA to 2.7 A (1 A=0.1 nm) resolution. The latter reveals the organization of the selectivity filter to be similar to that of M. jannaschii CorA and also the previously unknown organization of the second signature motif of the CorA family. The proposed gating is achieved by a helical rotation upon the binding of a metal ion substrate to the regulatory binding sites. Additionally, our data suggest that the preference of this CorA for Co2+ over Mg2+ is controlled by the presence of threonine side chains in the channel. Finally, the roles of the intracellular metal-binding sites have been assigned to increased thermostability and regulation of the gating. These mechanisms most likely apply to the entire CorA family as they are regulated by the highly conserved amino acids.
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co2 selectivity of thermotoga maritima cora and its inability to regulate mg2 homeostasis present a new class of cora proteins
Journal of Biological Chemistry, 2011Co-Authors: Yu Xia, Newsha Sahaf, Annakarin Lundback, Gustav Nordlund, Peter Brzezinski, Said EshaghiAbstract:CorA is a family of divalent cation transporters ubiquitously present in bacteria and archaea. Although CorA can transport both Mg(2+) and Co(2+) almost equally well, its main role has been suggest ...
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co2 selectivity of thermotoga maritima cora and its inability to regulate mg2 homeostasis present a new class of cora proteins
Journal of Biological Chemistry, 2011Co-Authors: Yu Xia, Newsha Sahaf, Annakarin Lundback, Gustav Nordlund, Peter Brzezinski, Said EshaghiAbstract:CorA is a family of divalent cation transporters ubiquitously present in bacteria and archaea. Although CorA can transport both Mg2+ and Co2+ almost equally well, its main role has been suggested to be that of primary Mg2+ transporter of prokaryotes and hence the regulator of Mg2+ homeostasis. The reason is that the affinity of CorA for Co2+ is relatively low and thus considered non-physiological. Here, we show that Thermotoga maritima CorA (TmCorA) is incapable of regulating the Mg2+ homeostasis and therefore cannot be the primary Mg2+ transporter of T. maritima. Further, our in vivo experiments confirm that TmCorA is a highly selective Co2+ transporter, as it selects Co2+ over Mg2+ at >100 times lower concentrations. In addition, we present data that show TmCorA to be extremely thermostable in the presence of Co2+. Mg2+ could not stabilize the protein to the same extent, even at high concentrations. We also show that addition of Co2+, but not Mg2+, specifically induces structural changes to the protein. Altogether, these data show that TmCorA has the role of being the transporter of Co2+ but not Mg2+. The physiological relevance and requirements of Co2+ in T. maritima is discussed and highlighted. We suggest that CorA may have different roles in different organisms. Such functional diversity is presumably a reflection of minor, but important structural differences within the CorA family that regulate the gating, substrate selection, and transport.
Bradley H Shaffer - One of the best experts on this subject based on the ideXlab platform.
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species boundaries and phylogenetic relationships in the critically endangered asian box turtle genus Cuora
Molecular Phylogenetics and Evolution, 2012Co-Authors: Phillip Q Spinks, Robert C Thomson, Yaping Zhang, Jing Che, Bradley H ShafferAbstract:Abstract Turtles are currently the most endangered major clade of vertebrates on earth, and Asian box turtles ( Cuora ) are in catastrophic decline. Effective management of this diverse turtle clade has been hampered by human-mediated, and perhaps natural hybridization, resulting in discordance between mitochondrial and nuclear markers and confusion regarding species boundaries and phylogenetic relationships among hypothesized species of Cuora . Here, we present analyses of mitochondrial and nuclear DNA data for all 12 currently hypothesized species to resolve both species boundaries and phylogenetic relationships. Our 15-gene, 40-individual nuclear data set was frequently in conflict with our mitochondrial data set; based on its general concordance with published morphological analyses and the strength of 15 independent estimates of evolutionary history, we interpret the nuclear data as representing the most reliable estimate of species boundaries and phylogeny of Cuora . Our results strongly reiterate the necessity of using multiple nuclear markers for phylogeny and species delimitation in these animals, including any form of DNA “barcoding”, and point to Cuora as an important case study where reliance on mitochondrial DNA can lead to incorrect species identification.
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(Testudines, Geoemydidae) and a plea for taxonomic stability
2011Co-Authors: Phillip Q Spinks, Robert C Thomson, Bradley H ShafferAbstract:We analyze the phylogenetic variation present in the Cuora trifasciata species complex using mitochondrial and nuclear DNA sequence data. We use this information to evaluate the recent description of Cuora cyclornata Blanck, McCord, and Le (2006), and reinterpret this proposed species in light of likely mitochondrial introgression. Our results indicate that the pattern of variation within the Cuora trifasciata species complex is better explained by mitochondrial introgression coupled with hybridization and/or clinal variation, than it is by the presence of a previously unrecognized species. We also use our phylogeny as a framework for discussion of additional proposed changes to generic level taxonomy in this critically imperiled clade. Our results highlight the importance of appropriate data sampling in taxonomic revisions and suggest that Cuora cyclornata be treated as a junior synonym of Cuora trifasciata
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a reassessment of Cuora cyclornata blanck mccord and le 2006 testudines geoemydidae and a plea for taxonomic stability
Zootaxa, 2009Co-Authors: Phillip Q Spinks, Robert C Thomson, Bradley H ShafferAbstract:We analyze the phylogenetic variation present in the Cuora trifasciata species complex using mitochondrial and nuclear DNA sequence data. We use this information to evaluate the recent description of Cuora cyclornata Blanck, McCord, and Le (2006), and reinterpret this proposed species in light of likely mitochondrial introgression. Our results indicate that the pattern of variation within the Cuora trifasciata species complex is better explained by mitochondrial introgression coupled with hybridization and/or clinal variation, than it is by the presence of a previously unrecognized species. We also use our phylogeny as a framework for discussion of additional proposed changes to generic level taxonomy in this critically imperiled clade. Our results highlight the importance of appropriate data sampling in taxonomic revisions and suggest that Cuora cyclornata be treated as a junior synonym of Cuora trifasciata.
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conservation phylogenetics of the asian box turtles geoemydidae Cuora mitochondrial introgression numts and inferences from multiple nuclear loci
Conservation Genetics, 2007Co-Authors: Phillip Q Spinks, Bradley H ShafferAbstract:Asian box turtles (genus Cuora, family Geoemydidae) comprise a clade of 12 aquatic and semiaquatic nominate species distributed across southern China and Southeast Asia. Over the last two decades, turtles throughout Asia have been harvested at an unsustainable rate to satisfy demands for food, traditional Chinese medicine, and the pet trade. Con- sequently, all species of Cuora were recently placed on the IUCN Red List, nine are currently listed as criti- cally endangered by the IUCN, and all species are listed in Appendix II of CITES. We compiled a 67-specimen mitochondrial (~1,650 base pairs (bp) from two mitochondrial genes) and a 40-specimen nuclear-plus-mitochondrial (~3,900 bp total, three nuclear introns plus an additional ~860 bp mitochon- drial gene fragment) DNA data set to reconstruct the phylogeny of Cuora species and to assess genetic diversity and species boundaries for several of the most problematic taxa. Our sampling included 23 C. trifas- ciata ,1 7C. zhoui and 1-4 individuals of the remaining 10 species of Cuora. Maximum likelihood, maximum parsimony and Bayesian analyses all recovered similar, well resolved trees. Within the Cuora clade, mito- chondrial and nuclear sequence data indicated that both C. zhoui and C. mccordi represent old lineages with little or no history of interspecific gene flow, suggesting that they are good genealogical species. Based on mtDNA, Cuora pani was paraphyletic and C. trifasciata was composed of two highly divergent lineages that were not each other's closest relatives; both cases of non-monophyly were due to a mtDNA sequence that was widespread and identical in C. aurocapitata, C. pani and C. trifasciata. However, when combined with nuclear DNA results, our data indicate that C. trifasciata is a single, monophyletic taxon, and that mitochondrial introgression and nuclear-mitochondrial pseudogenes have led to a complex pattern of mitochondrial gene relationships that does not reflect species-level histories. Our results imply that captive ''assurance colonies'' of both C. trifasciata and C. pani should be genotyped to identify pure, non-hybrid members of both taxa, and we recommend that introgressed and pure taxa be man- aged as independent entities until the full evolutionary histories of these critically endangered turtles are resolved.
Newsha Sahaf - One of the best experts on this subject based on the ideXlab platform.
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exploring the structure and function of thermotoga maritima cora reveals the mechanism of gating and ion selectivity in co2 mg2 transport
Biochemical Journal, 2013Co-Authors: Nurhuda Nordin, Albert Guskov, Terri Phua, Newsha Sahaf, Yu Xia, Hojjat Eshaghi, Said EshaghiAbstract:The CorA family of divalent cation transporters utilizes Mg2+ and Co2+ as primary substrates. The molecular mechanism of its function, including ion selectivity and gating, has not been fully characterized. Recently we reported a new structure of a CorA homologue from Methanocaldococcus jannaschii, which provided novel structural details that offered the conception of a unique gating mechanism involving conversion of an open hydrophilic gate into a closed hydrophobic one. In the present study we report functional evidence for this novel gating mechanism in the Thermotoga maritima CorA together with an improved crystal structure of this CorA to 2.7 A (1 A=0.1 nm) resolution. The latter reveals the organization of the selectivity filter to be similar to that of M. jannaschii CorA and also the previously unknown organization of the second signature motif of the CorA family. The proposed gating is achieved by a helical rotation upon the binding of a metal ion substrate to the regulatory binding sites. Additionally, our data suggest that the preference of this CorA for Co2+ over Mg2+ is controlled by the presence of threonine side chains in the channel. Finally, the roles of the intracellular metal-binding sites have been assigned to increased thermostability and regulation of the gating. These mechanisms most likely apply to the entire CorA family as they are regulated by the highly conserved amino acids.
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co2 selectivity of thermotoga maritima cora and its inability to regulate mg2 homeostasis present a new class of cora proteins
Journal of Biological Chemistry, 2011Co-Authors: Yu Xia, Newsha Sahaf, Annakarin Lundback, Gustav Nordlund, Peter Brzezinski, Said EshaghiAbstract:CorA is a family of divalent cation transporters ubiquitously present in bacteria and archaea. Although CorA can transport both Mg(2+) and Co(2+) almost equally well, its main role has been suggest ...
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co2 selectivity of thermotoga maritima cora and its inability to regulate mg2 homeostasis present a new class of cora proteins
Journal of Biological Chemistry, 2011Co-Authors: Yu Xia, Newsha Sahaf, Annakarin Lundback, Gustav Nordlund, Peter Brzezinski, Said EshaghiAbstract:CorA is a family of divalent cation transporters ubiquitously present in bacteria and archaea. Although CorA can transport both Mg2+ and Co2+ almost equally well, its main role has been suggested to be that of primary Mg2+ transporter of prokaryotes and hence the regulator of Mg2+ homeostasis. The reason is that the affinity of CorA for Co2+ is relatively low and thus considered non-physiological. Here, we show that Thermotoga maritima CorA (TmCorA) is incapable of regulating the Mg2+ homeostasis and therefore cannot be the primary Mg2+ transporter of T. maritima. Further, our in vivo experiments confirm that TmCorA is a highly selective Co2+ transporter, as it selects Co2+ over Mg2+ at >100 times lower concentrations. In addition, we present data that show TmCorA to be extremely thermostable in the presence of Co2+. Mg2+ could not stabilize the protein to the same extent, even at high concentrations. We also show that addition of Co2+, but not Mg2+, specifically induces structural changes to the protein. Altogether, these data show that TmCorA has the role of being the transporter of Co2+ but not Mg2+. The physiological relevance and requirements of Co2+ in T. maritima is discussed and highlighted. We suggest that CorA may have different roles in different organisms. Such functional diversity is presumably a reflection of minor, but important structural differences within the CorA family that regulate the gating, substrate selection, and transport.
