The structure of Mn(II)-bound Rubisco from Spinacia oleracea.

The rate of photosynthesis and, thus, CO fixation, is limited by the rate of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Not only does Rubisco have a relatively low catalytic rate, but it also is promiscuous regarding the metal identity in the active site of the large subunit. In Nature, Rubisco binds either Mg(II) or Mn(II), depending on the chloroplastic ratio of these metal ions; most studies performed with Rubisco have focused on Mg-bound Rubisco.

Outer coordination sphere influences on cofactor maturation and substrate oxidation by cytochrome P460.

Product selectivity of ammonia oxidation by ammonia-oxidizing bacteria (AOB) is tightly controlled by metalloenzymes. Hydroxylamine oxidoreductase (HAO) is responsible for the oxidation of hydroxylamine (NHOH) to nitric oxide (NO). The non-metabolic enzyme cytochrome (cyt) P460 also oxidizes NHOH, but instead produces nitrous oxide (NO).

Defects Formation and Amorphization of Zn-MOF-74 Crystals by Post-Synthetic Interactions with Bidentate Adsorbates.

The controlled introduction of defects into MOFs is a powerful strategy to induce new physiochemical properties and improve their performance for target applications. Herein, we present a new strategy for defect formation and amorphization of the canonical MOF-74 frameworks based on fine-tuning of adsorbate-framework interactions in the metal congener, hence introducing structural defects. Specifically, we demonstrate that controlled interactions between the MOF and bidentate ligands adsorbed in the pores initiates defect formation and eventual amorphization of the crystal.

Cdc42 functions as a regulatory node for tumour-derived microvesicle biogenesis.

Tumour-derived microvesicles (MVs) serve as critical mediators of cell-to-cell communication in the tumour microenvironment. So far, the underlying mechanisms of MV biogenesis, especially how key tumorigenesis signals such as abnormal EGF signalling regulates MV release, remain unclear. Here, we set out to establish reliable readouts for MV biogenesis and then explore the molecular mechanisms that regulate MV generation.

Scrutinizing metal-ligand covalency and redox non-innocence nitrogen K-edge X-ray absorption spectroscopy.

Nitrogen K-edge X-ray absorption spectra (XAS) were obtained for 19 transition metal complexes bearing bipyridine, ethylenediamine, ammine, and nitride ligands. Time-dependent density functional theory (TDDFT) and DFT/restricted open configuration interaction singles (DFT/ROCIS) calculations were found to predict relative N K-edge XAS peak energies with good fidelity to experiment. The average difference (|Δ|) between experimental and linear corrected calculated energies were found to be 0.

Self-Triggered Apoptosis Enzyme Prodrug Therapy (STAEPT): Enhancing Targeted Therapies via Recurrent Bystander Killing Effect by Exploiting Caspase-Cleavable Linker.

Tumor heterogeneity is associated with the therapeutic failures of targeted therapies. To overcome such heterogeneity, a novel targeted therapy is proposed that could kill tumor populations with diverse phenotypes by delivering nonselective cytotoxins to target-positive cells as well as to the surrounding tumor cells via a recurrent bystander killing effect. A representative prodrug is prepared that targets integrin αvβ3 and releases cytotoxins upon entering cells or by caspase-3.

Solvothermal-Derived S-Doped Graphene as an Anode Material for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have attracted enormous attention in recent years due to the high abundance and low cost of sodium. However, in contrast to lithium-ion batteries, conventional graphite is unsuitable for SIB anodes because it is much more difficult to intercolate the larger Na ions into graphite layers. Therefore, it is critical to develop new anode materials for SIBs for practical use.

STIM1 activation is regulated by a 14 amino acid sequence adjacent to the CRAC activation domain.

Oligomerization of the Ca sensor, STIM1, in the endoplasmic reticulum (ER) membrane, caused by depletion of ER Ca stores, results in STIM1 coupling to the plasma membrane Ca channel protein, Orai1, to activate Ca influx in a process known as store-operated Ca entry. We use fluorimetry-based fluorescence resonance energy transfer (FRET) to monitor changes in STIM1 oligomerization in COS7 cells transfected with STIM1 constructs containing selected truncations, deletions, and point mutations, and labeled with donor and acceptor fluorescent proteins at either the luminal (N-terminal) or the cytoplasmic (C-terminal) ends. Our results with sequential truncations of STIM1 from the C-terminus support previous evidence that the CRAC activation domain (CAD/SOAR, human sequence 342-448) is an oligomer-promoting segment of STIM1, and they show that truncation just after CAD/SOAR (1-448) causes significantly elevated basal cytoplasmic Ca and spontaneous STIM1 clustering.

A fluorimetric readout reporting the kinetics of nucleotide-induced human ribonucleotide reductase oligomerization.

Human ribonucleotide reductase (hRNR) is a target of nucleotide chemotherapeutics in clinical use. The nucleotide-induced oligomeric regulation of hRNR subunit α is increasingly being recognized as an innate and drug-relevant mechanism for enzyme activity modulation. In the presence of negative feedback inhibitor dATP and leukemia drug clofarabine nucleotides, hRNR-α assembles into catalytically inert hexameric complexes, whereas nucleotide effectors that govern substrate specificity typically trigger α-dimerization.

The enzymology of nitric oxide in bacterial pathogenesis and resistance.

Mammalian NOSs (nitric oxide synthases) are haem-based monoxygenases that oxidize the amino acid arginine to the intracellular signal and protective cytotoxin nitric oxide (NO). Certain strains of mostly Gram-positive bacteria contain homologues of the mammalian NOS catalytic domain that can act as NOSs when suitable reductants are supplied. Crystallographic analyses of bacterial NOSs, with substrates and haem-ligands, have disclosed important features of assembly and active-centre chemistry, both general to the NOS family and specific to the bacterial proteins.

Ca(11)N(6)(CN(2))(2) and Ca(4)N(2)(CN(2)): The True Nature of an "Unusual Binary Nitride" Is Finally Revealed.

One calcium nitride less! Several different binary nitrides of calcium have been reported: Ca(3)N(2), Ca(2)N, Ca(3)N(4), and Ca(11)N(8). X-ray structural analysis and spectroscopy revealed the latter is actually calcium nitride cyanamide and one of, so far, two examples of a new class of ternary phases (see boxes in the phase diagram).

X-ray crystal structure of aminoimidazole ribonucleotide synthetase (PurM), from the Escherichia coli purine biosynthetic pathway at 2.5 A resolution.

Background: The purine biosynthetic pathway in procaryotes enlists eleven enzymes, six of which use ATP. Enzymes 5 and 6 of this pathway, formylglycinamide ribonucleotide (FGAR) amidotransferase (PurL) and aminoimidazole ribonucleotide (AIR) synthetase (PurM) utilize ATP to activate the oxygen of an amide within their substrate toward nucleophilic attack by a nitrogen. AIR synthetase uses the product of PurL, formylglycinamidine ribonucleotide (FGAM) and ATP to make AIR, ADP and P(i).

The crystal structure of pyrimidine nucleoside phosphorylase in a closed conformation.

Background: Pyrimidine nucleoside phosphorylase (PYNP) catalyzes the reversible phosphorolysis of pyrimidines in the nucleotide synthesis salvage pathway. In lower organisms (e.g.