Manganese activation of superoxide dismutase 2 in
            <i>Saccharomyces cerevisiae</i>
            requires
            <i>MTM1</i>
            , a member of the mitochondrial carrier family

Luk, Ed; Carroll, Mark; Baker, Michelle; Culotta, Valeria C.

doi:10.1073/pnas.1632471100

Cited by 136 publications

(159 citation statements)

References 41 publications

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“…Leu5p also has a contact point II predicting adenine nucleotide binding, which is consistent with it being the coenzyme A carrier (33). Mtm1p, which is proposed to transport a manganese cofactor (34), has a contact point II typical of an amino acid carrier, and the proposed iron transporters Mrs3p and Mrs4p (35) share a novel M-N motif at contact point II, suggesting that they transport neither nucleotides nor keto acids or amino acids and could form a distinct subfamily transporting coordinated iron. The residues at contact point II of Rim2p, YEL006w, and YPR011c are typical of adenine nucleotide carriers, those of YDL119c, Ymc1p, and YMR166c are characteristic of amino acid carriers, and that of Ymc2p, which is homologous to Ymc1p, is similar to that of a keto acid carrier.…”

Section: Resultsmentioning

confidence: 59%

Mitochondrial carriers in the cytoplasmic state have a common substrate binding site

Robinson

Kunji

2006

Proc. Natl. Acad. Sci. U.S.A.

234

289

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Mitochondrial carriers link biochemical pathways in the cytosol and mitochondrial matrix by transporting substrates across the inner mitochondrial membrane. Substrate recognition is specific for each carrier, but sequence similarities suggest the carriers have similar structures and mechanisms of substrate translocation. By considering conservation of amino acids, distance and chemical constraints, and by modeling family members on the known structure of the ADP͞ATP translocase, we have identified a common substrate binding site. It explains substrate selectivity and proton coupling and provides a mechanistic link to carrier opening by substrate-induced perturbation of the salt bridges that seal the pathway to and from the mitochondrial matrix. It enables the substrate specificity of uncharacterized mitochondrial carriers to be predicted.comparative modeling ͉ membrane protein ͉ sequence alignment M embers of the mitochondrial carrier family are located in the inner mitochondrial membrane and allow exchange of substrates between the cytosol and the mitochondrial matrix (1). The family is exclusive to eukaryotes, and its members are unrelated to other transporter families, including the major facilitator superfamily and the ABC transporters. Their substrates include nucleotides, amino acids, cofactors, carboxylic acids, and inorganic anions required by the organelle for oxidative phosphorylation, gluconeogenesis, synthesis and degradation of amino and fatty acids, macromolecular synthesis of proteins and nucleic acids, sterol metabolism, and thermogenesis (1). Mutations of the carriers are associated with diseases, including progressive external opthalmoplegia, adult-and neonatal-onset type II citrullinaemia, Amish-type microcephaly, hyperornithinemia-hyperammonia-homocitrullinuria, carnitineacylcarnitine translocase deficiency, neonatal myoclonic epilepsy, severe obesity, and type II diabetes (1).The mitochondrial carriers have three tandem repeats of Ϸ100 aa, each containing two transmembrane ␣-helices linked by a large loop (2) and a conserved signature motif P-X-[DE]-X-X-[RK] (3). The carriers exist in two distinct conformational states: the cytoplasmic state (c-state) in which the carrier accepts its substrate from the cytoplasm, and the matrix state in which it accepts a substrate from the mitochondrial matrix. For the ADP͞ATP carrier, the inhibitor carboxyatractyloside (CATR) is known to bind to the carrier in the c-state only and prevent the binding of ADP. In the atomic model of the ADP͞ATP carrier 1 from Bos taurus (BtAAC1) in complex with CATR (4), the six-transmembrane ␣-helices form a barrel that has pseudo-3-fold symmetry. CATR is bound in the internal aqueous cavity (see Fig. 4, which is published as supporting information on the PNAS web site), which is open to the cytosol and closed to the mitochondrial matrix, consistent with the structure representing the c-state. The prolines of the signature motif kink the transmembrane helices, bringing their C-terminal ends together at the base of the cavit...

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Section: Resultsmentioning

confidence: 59%

Mitochondrial carriers in the cytoplasmic state have a common substrate binding site

Robinson

Kunji

2006

Proc. Natl. Acad. Sci. U.S.A.

234

289

View full text Add to dashboard Cite

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“…If the mitochondrial copper transporter translocates multiple metal ions, the mitochondrion may have a buffering capacity for diverse metal ions. Cells lacking Mtm1 show no Sod2 activity, but mitochondrial Mn(II) levels are normal (54). Thus, mtm1⌬ cells are expected to contain a pool of non Sod2-bound Mn(II).…”

Section: Discussionmentioning

confidence: 99%

Yeast Contain a Non-proteinaceous Pool of Copper in the Mitochondrial Matrix

Cobine

Ojeda

Rigby

et al. 2004

Journal of Biological Chemistry

202

199

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The yeast mitochondrion is shown to contain a pool of copper that is distinct from that associated with the two known mitochondrial cuproenzymes, superoxide dismutase (Sod1) and cytochrome c oxidase (CcO) and the copper-binding CcO assembly proteins Cox11, Cox17, and Sco1. Only a small fraction of mitochondrial copper is associated with these cuproproteins. The bulk of the remainder is localized within the matrix as a soluble, anionic, low molecular weight complex. The identity of the matrix copper ligand is unknown, but the bulk of the matrix copper fraction is not protein-bound. The mitochondrial copper pool is dynamic, responding to changes in the cytosolic copper level. The addition of copper salts to the growth medium leads to an increase in mitochondrial copper, yet the expansion of this matrix pool does not induce any respiration defects. The matrix copper pool is accessible to a heterologous cuproenzyme. Co-localization of human Sod1 and the metallochaperone CCS within the mitochondrial matrix results in suppression of growth defects of sod2⌬ cells. However, in the absence of CCS within the matrix, the activation of human Sod1 can be achieved by the addition of copper salts to the growth medium.Copper is an essential cell nutrient acting as a cofactor in nearly 20 enzymes (1). However, excess accumulation of copper ions results in toxicity. Evidence for the effectiveness of copper ions as a toxin comes from its historic use as a fungicide, molluscide, and algicide. Homeostatic mechanisms exist in cells to regulate the cellular concentration of copper ions, thus maintaining copper balance and minimizing deleterious effects. Cells appear to maintain a quota for essential metal ions; this quota is primarily the quantity necessary to metallate the various copper proteins (2, 3). Copper ions are required for at least three key enzymes in Saccharomyces cerevisiae. The cuproenzymes include the cytosolic superoxide dismutase Sod1, 1 the plasma membrane ferroxidase Fet3, and the mitochondrial inner membrane enzyme cytochrome c oxidase (CcO). The copper quota of the yeast S. cerevisiae is about 5 ϫ 10 5 atoms per cell (3, 4).It is unclear what fraction of the 5 ϫ 10 5 copper atoms per cell is from copper in Sod1, Fet3, and CcO. Expression of these copper-binding proteins varies with growth conditions, suggesting that the copper may be distributed differently depending on growth conditions. Clearly, a significant fraction of the cellular copper is associated with Sod1; however, not all Sod1 molecules are metallated (4, 5). Fet3 requires four copper ions for activity, but levels of this protein are dependent on iron status of the medium (6). CcO levels vary depending on whether the cells are grown by fermentation or respiration. In addition, a varying quantity of cellular copper exists bound to two metallothioneins, Cup1 and Crs5 (7,8). Expression of CUP1 and CRS5 is regulated by copper levels through the copper-responsive transcription factor Ace1 (9, 10). An increase in the free Cu(I) ion pool activates Ace1 throu...

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“…In a screen for genes involved in Mn(II) uptake into mitochondria, a mitochondrial carrier protein designated Mtm1 was identified as a key component for metallation of Sod2 in the matrix (Luk et al 2003a). Cells lacking Mtm1 are devoid of MnSod2 activity, but activity is restored by supplementation of cultures with high exogenous Mn(II) salts.…”

Section: Protein Metallation Within the Mitochondrionmentioning

confidence: 99%

“…Cells lacking Mtm1 are devoid of MnSod2 activity, but activity is restored by supplementation of cultures with high exogenous Mn(II) salts. Since mitochondrial Mn(II) levels are not depleted in mtm1Δ cells, the suggestion was made that Mtm1 had a role in Mn(II) trafficking to Sod2 within the matrix during the folding reaction (Luk et al 2003a). Since metallation of Sod2 is coupled to protein folding, the metallation step may occur as the Sod2 polypeptide is emerging during import across the IM.…”

Section: Protein Metallation Within the Mitochondrionmentioning

confidence: 99%