Crystal structures of a dodecameric multicopper oxidase from Marinithermus hydrothermalis

Multicopper oxidases (MCOs) represent a diverse family of enzymes that catalyze the oxidation of either an organic or a metal substrate with concomitant reduction of dioxygen to water. These enzymes contain variable numbers of cupredoxin domains, two, three or six per subunit, and rely on four copper ions, a single type I copper and three additional copper ions organized in a trinuclear cluster (TNC), with one type II and two type III copper ions, to catalyze the reaction. Here, two crystal structures and the enzymatic characterization of Marinithermus hydrothermalis MCO, a two-domain enzyme, are reported. This enzyme decolorizes Congo Red dye at 70°C in the presence of high halide concentrations and may therefore be useful in the detoxification of industrial waste that contains dyes. In two distinct crystal structures, MhMCO forms the trimers seen in other two-domain MCOs, but differs from these enzymes in that four trimers interact to create a dodecamer. This dodecamer of MhMCO forms a closed ball-like structure and has implications for the sequestration of bound divalent metal ions as well as substrate accessibility. In each subunit of the dodecameric structures, a Trp residue, Trp351, located between the type I and TNC sites exists in two distinct conformations, consistent with a potential role in facilitating electron transfer in the enzyme.

Metal−organic frameworks of linear trinuclear cluster secondary building units: Structures and applications

Secondary building units (SBUs) in metal−organic frameworks (MOFs) are essential from both a structural and performance perspective. While a variety of SBUs, such as paddlewheel CuII2, triangular CrIII3, tetrahedral ZnII4,...

A novel luminescent ionic trinuclear Cu3I2 cluster cuprous complex supported by a P^N ligand: synthesis, structure characterization, properties and TD–DFT calculations

Luminescent cuprous complexes are an important class of coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The title ionic trinuclear Cu3I2 complex, tris[μ2-diphenyl(pyridin-2-yl)phosphane-κ2 P:N]di-μ3-iodido-tricopper(I)(3 Cu—Cu) hexafluoridophosphate, [Cu3I2(C39H32NP)3]PF6, conventionally abbreviated as [Cu3I2(Ph2PPy)3]PF6, is described. Each CuI atom is coordinated by two μ3-iodide ligands and by a P and an N atom from two Ph2PPy ligands, giving rise to a CuI2PN tetrahedral coordination geometry about each CuI centre. The electronic absorption and photoluminescence properties of this trinuclear cluster have been studied on as-synthesized samples, which had been examined previously by powder X-ray diffraction. A detailed time-dependent density functional theory (TD–DFT) study was carried out and showed a green emission derived from a halide-to-ligand charge transfer and metal-to-ligand charge transfer 3(X+M)LCT excited state.