The deduced protein product of open reading frame slr0946 from Synechocystis sp. strain PCC 6803, SynArsC, contains the conserved sequence features of the enzyme superfamily that includes the low-molecularweight protein-tyrosine phosphatases and the Staphylococcus aureus pI258 ArsC arsenate reductase. The recombinant protein product of slr0946, rSynArsC, exhibited vigorous arsenate reductase activity (V max ‫؍‬ 3.1 mol/min ⅐ mg), as well as weak phosphatase activity toward p-nitrophenyl phosphate (V max ‫؍‬ 0.08 mol/ min ⅐ mg) indicative of its phosphohydrolytic ancestry. pI258 ArsC from S. aureus is the prototype of one of three distinct families of detoxifying arsenate reductases. The prototypes of the others are Acr2p from Saccharomyces cerevisiae and R773 ArsC from Escherichia coli. All three have converged upon catalytic mechanisms involving an arsenocysteine intermediate. While SynArsC is homologous to pI258 ArsC, its catalytic mechanism exhibited a unique combination of features. rSynArsC employed glutathione and glutaredoxin as the source of reducing equivalents, like Acr2p and R773 ArsC, rather than thioredoxin, as does the S. aureus enzyme. As postulated for Acr2p and R773 ArsC, rSynArsC formed a covalent complex with glutathione in an arsenate-dependent manner. rSynArsC contains three essential cysteine residues like pI258 ArsC, whereas the yeast and E. coli enzymes require only one cysteine for catalysis. As in the S. aureus enzyme, these "extra" cysteines apparently shuttle a disulfide bond to the enzyme's surface to render it accessible for reduction. SynArsC and pI258 ArsC thus appear to represent alternative branches in the evolution of their shared phosphohydrolytic ancestor into an agent of arsenic detoxification.Arsenate and related compounds (e.g., arsenite, antomite) are naturally occurring, broadly acting toxins frequently encountered at biologically deleterious concentrations in the environment (reviewed in reference 44). The strong chemical parallels between phosphorous and arsenic, which reside in the same column of the periodic table, limit the ability of phosphate transport systems to discriminate between this vital nutrient and arsenate (45), thus exacerbating the latter's toxic potential. Microorganisms combat the collateral importation of arsenate by a two-step mechanism in which this compound is first reduced to arsenite. Although arsenite is a more potent toxicant than arsenate, the former can be selectively banished from the cell's interior through the intervention of a dedicated, inducible transporter.While the basic strategy for conferring arsenical resistance is broadly conserved among microorganisms, the arsenate reductases responsible for catalyzing the conversion of arsenate to arsenite are not. To date, three "detoxifying" arsenate reductases have been identified and characterized in molecular detail: Acr2p from the microbial eukaryote Saccharomyces cerevisiae (2), ArsC encoded by plasmid R773 from the gramnegative bacterium Escherichia coli (R773 ArsC) (7), and ArsC encod...

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The eukaryotic protein kinase (ePK) paradigm provides integral components for signal transduction cascades throughout nature. However, while so-called typical ePKs permeate the Eucarya and Bacteria, atypical ePKs dominate the kinomes of the Archaea. Intriguingly, the catalytic domains of the handful of deduced typical ePKs from the archaeon Sulfolobus solfataricus P2 exhibit significant resemblance to the protein kinases that phosphorylate translation initiation factor 2α (eIF2α) in response to cellular stresses. We cloned and expressed one of these archaeal eIF2α protein kinases, SsoPK4. SsoPK4 exhibited protein-serine/threonine kinase activity toward several proteins, including the S. solfataricus homolog of eIF2α, aIF2α. The activity of SsoPK4 was inhibited in vitro by 3ʹ,5ʹ-cyclic AMP (Ki of ~23 µM) and was activated by oxidized Coenzyme A, an indicator of oxidative stress in the Archaea. Activation enhanced the apparent affinity for protein substrates, Km, but had little effect on Vmax. Autophosphorylation activated SsoPK4 and rendered it insensitive to oxidized Coenzyme A.

The transition to a remote teaching and learning environment was quick and painful at times, and yet it was a learning experience for everyone. The chemists at Centre College utilized new (to them) technology to reimagine the typical face to face interactions with students and colleagues. From Slack to Pear Deck to Zoom classrooms, the faculty and students engaged with a variety of platforms to continue to learn remotely despite the challenges of the global pandemic. The faculty learned the value of utilizing different types of technology, and the students learned some important skills and content.

This communication summarizes one of the invited papers to the Flipped Classroom ACS Division of Chemical Education Committee on Computers in Chemical Education online ConfChem held from May 18 to June 24, 2014. Just in TimeTeaching is a technique in which students read the material before class and respond to a few questions. In a first-year seminar course, The Chemistry of Food, students were assigned to maintain blogs for the entire CentreTerm, a 16-day term. To create an online learning community, the instructor's blog in lieu of a quiz was used as a forum to assign the readings and pose questions about the readings. The comments on the instructor blog, as well as individual student posts, were used to develop the classroom discussion; moreover, many of the readings were not discussed in class but entirely online. Many students who would not normally participate in class were more than willing to participate online, thus providing the class discussion with more variety and greater input from the students.