Yeast copper–zinc superoxide dismutase can be activated in the absence of its copper chaperone

Copper-zinc superoxide dismutase (Sod1) is an abundant intracellular enzyme that catalyzes the disproportionation of superoxide to give hydrogen peroxide and dioxygen. In most organisms, Sod1 acquires copper by a combination of two pathways, one dependent on the copper chaperone for Sod1 (CCS), and the other independent of CCS. Examples have been reported of two exceptions: Saccharomyces cerevisiae, in which Sod1 appeared to be fully dependent on CCS, and Caenorhabditis elegans, in which Sod1 was completely independent of CCS. Here, however, using overexpressed Sod1, we show there is also a significant amount of CCS-independent activation of S. cerevisiae Sod1, even in low-copper medium. In addition, we show CCS-independent oxidation of the disulfide bond in S. cerevisiae Sod1. There appears to be a continuum between CCS-dependent and CCS-independent activation of Sod1, with yeast falling near but not at the CCS-dependent end

Structure and Substrate Specificity of the Pyrococcal Coenzyme A Disulfide Reductases/Polysulfide Reductases (CoADR/Psr): Implications for S⁰‑Based Respiration and a Sulfur-Dependent Antioxidant System in <i>Pyrococcus</i>

FAD and NAD­(P)­H-dependent coenzyme A disulfide reductases/polysulfide reductases (CoADR/Psr) have been proposed to be important for the reduction of sulfur and disulfides in the sulfur-reducing anaerobic hyperthermophiles <i>Pyrococcus horikoshii</i> and <i>Pyrococcus furiosus</i>; however, the form(s) of sulfur that the enzyme actually reduces are not clear. Here we determined the structure for the FAD- and coenzyme A-containing holoenzyme from <i>P. horikoshii</i> to 2.7 Å resolution and characterized its substrate specificity. The enzyme is relatively promiscuous and reduces a range of disulfide, persulfide, and polysulfide compounds. These results indicate that the likely <i>in vivo</i> substrates are NAD­(P)H and di-, poly-, and persulfide derivatives of coenzyme A, although polysulfide itself is also efficiently reduced. The role of the enzyme in the reduction of elemental sulfur (S₈) <i>in situ</i> is not, however, ruled out by these results, and the possible roles of this substrate are discussed. During aerobic persulfide reduction, rapid recycling of the persulfide substrate was observed, which is proposed to occur via sulfide oxidation by O₂ and/or H₂O₂. As expected, this reaction disappears under anaerobic conditions and may explain observations by others that CoADR is not essential for S⁰ respiration in <i>Pyrococcus</i> or <i>Thermococcus</i> but appears to participate in oxidative defense in the presence of S⁰. When compared to the homologous Npsr enzyme from <i>Shewanella loihica</i> PV-4 and homologous enzymes known to reduce CoA disulfide, the <i>ph</i>CoADR structure shows a relatively restricted substrate channel leading into the sulfur-reducing side of the FAD isoalloxazine ring, suggesting how this enzyme class may select for specific disulfide substrates

Yeast copper–zinc superoxide dismutase can be activated in the absence of its copper chaperone

Copper–zinc superoxide dismutase (Sod1) is an abundant intracellular enzyme that catalyzes the disproportionation of superoxide to give hydrogen peroxide and dioxygen. In most organisms, Sod1 acquires copper by a combination of two pathways, one dependent on the copper chaperone for Sod1 (CCS), and the other independent of CCS. Examples have been reported of two exceptions: Saccharomyces cerevisiae, in which Sod1 appeared to be fully dependent on CCS, and Caenorhabditis elegans, in which Sod1 was completely independent of CCS. Here, however, using overexpressed Sod1, we show there is also a significant amount of CCS-independent activation of S. cerevisiae Sod1, even in low-copper medium. In addition, we show CCS-independent oxidation of the disulfide bond in S. cerevisiae Sod1. There appears to be a continuum between CCS-dependent and CCS-independent activation of Sod1,with yeast falling near but not at the CCS-dependent end

Surface Ocean CO2 Atlas (SOCAT) V6

The Surface Ocean CO2 Atlas (SOCAT) is a synthesis activity by the international marine carbon research community (>100 contributors). SOCAT version 6 has 23.4 million quality-controlled, surface ocean fCO2 (fugacity of carbon dioxide) observations from 1957 to 2017 for the global oceans and coastal seas. Calibrated sensor data are also available. Automation allows annual, public releases. SOCAT data is discoverable, accessible and citable. SOCAT enables quantification of the ocean carbon sink and ocean acidification and evaluation of ocean biogeochemical models. SOCAT represents a milestone in biogeochemical and climate research and in informing policy. 424 datasets Version 5: https://doi.pangaea.de/10.1594/PANGAEA.877863 Version 4: https://doi.pangaea.de/10.1594/PANGAEA.866856 Version 3: https://doi.pangaea.de/10.1594/PANGAEA.849770 Version 2: https://doi.org/10.1594/PANGAEA.81515