Structure of the Mitochondrial Aminolevulinic Acid Synthase,a Key Heme Biosynthetic Enzyme

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Discovery of cell-active phenyl-imidazole Pin1 inhibitors by structure-guided fragment evolution

Pin1 is an emerging oncology target strongly implicated in Ras and ErbB2-mediated tumourigenesis. Pin1 isomerizes bonds linking phospho-serine/threonine moieties to proline enabling it to play a key role in proline-directed kinase signalling. Here we report a novel series of Pin1 inhibitors based on a phenyl imidazole acid core that contains sub-μM inhibitors. Compounds have been identified that block prostate cancer cell growth under conditions where Pin1 is essential.     

Comparative analysis of two slc11 (Nramp) loci in Takifugu rubripes

To study the evolution of the solute carrier family 11 (slc11; formerly Nramp) protein, we isolated and characterized two paralogs from the pufferfish Takifugu rubripes (Fugu). These teleost genes, designated Fugu slc11a-a and Fugu slc11a-b, comprise open reading frames of 1743 nucleotides (581 amino acids) and 1662 nt (554 aa), respectively. The proteins are 81% similar, and both exhibit signature features of the slc11 family of proteins including 12 transmembrane domains, a conserved transport motif and a glycosylated loop. Both Fugu paralogs are more Slc11a2-like based on sequence homology and phylogenetic studies. Analysis of gene environment placed both in the proximity of multiple loci syntenic to human chromosome 12q13, that is, within a SLC11A2 gene environment. However, Fugu slc11a-a also gave one match with chromosome 2q35, where human SLC11A1 resides. Functional diversification was suggested by differences in tissue distribution and subcellular localization. Fugu slc11a-a exhibits a restricted expression profile and a complex subcellular localization, including LAMP1 positive late endosomes/lysosomes in transiently transfected mouse macrophages. Fugu slc11a-b is expressed ubiquitously and localizes solely to late endosomes/lysosomes. This comparative analysis extends our understanding of the evolution and function of this important family of divalent cation transporters. [Sequence data from this article have been deposited with the EMBL/GenBank Data Libraries under accession nos. AJ496547/8/9 and AJ496550.]     

<Emphasis Type="Italic">Ochrobactrum</Emphasis> sp. MPV1 from a dump of roasted pyrites can be exploited as bacterial catalyst for the biogenesis of selenium and tellurium nanoparticles

Background

Bacteria have developed different mechanisms for the transformation of metalloid oxyanions to non-toxic chemical forms. A number of bacterial isolates so far obtained in axenic culture has shown the ability to bioreduce selenite and tellurite to the elemental state in different conditions along with the formation of nanoparticles—both inside and outside the cells—characterized by a variety of morphological features. This reductive process can be considered of major importance for two reasons: firstly, toxic and soluble (i.e. bioavailable) compounds such as selenite and tellurite are converted to a less toxic chemical forms (i.e. zero valent state); secondly, chalcogen nanoparticles have attracted great interest due to their photoelectric and semiconducting properties. In addition, their exploitation as antimicrobial agents is currently becoming an area of intensive research in medical sciences.

Results

In the present study, the bacterial strain Ochrobactrum sp. MPV1, isolated from a dump of roasted arsenopyrites as residues of a formerly sulfuric acid production near Scarlino (Tuscany, Italy) was analyzed for its capability of efficaciously bioreducing the chalcogen oxyanions selenite (SeO₃ ^2?) and tellurite (TeO₃ ^2?) to their respective elemental forms (Se⁰ and Te⁰) in aerobic conditions, with generation of Se- and Te-nanoparticles (Se- and TeNPs). The isolate could bioconvert 2 mM SeO₃ ^2? and 0.5 mM TeO₃ ^2? to the corresponding Se⁰ and Te⁰ in 48 and 120 h, respectively. The intracellular accumulation of nanomaterials was demonstrated through electron microscopy. Moreover, several analyses were performed to shed light on the mechanisms involved in SeO₃ ^2? and TeO₃ ^2? bioreduction to their elemental states. Results obtained suggested that these oxyanions are bioconverted through two different mechanisms in Ochrobactrum sp. MPV1. Glutathione (GSH) seemed to play a key role in SeO₃ ^2? bioreduction, while TeO₃ ^2? bioconversion could be ascribed to the catalytic activity of intracellular NADH-dependent oxidoreductases. The organic coating surrounding biogenic Se- and TeNPs was also characterized through Fourier-transform infrared spectroscopy. This analysis revealed interesting differences among the NPs produced by Ochrobactrum sp. MPV1 and suggested a possible different role of phospholipids and proteins in both biosynthesis and stabilization of such chalcogen-NPs.

Conclusions

In conclusion, Ochrobactrum sp. MPV1 has demonstrated to be an ideal candidate for the bioconversion of toxic oxyanions such as selenite and tellurite to their respective elemental forms, producing intracellular Se- and TeNPs possibly exploitable in biomedical and industrial applications.

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Targeting the Tumour Vasculature: Exploitation of Low Oxygenation and Sensitivity to NOS Inhibition by Treatment with a Hypoxic Cytotoxin

Many cancer research efforts focus on exploiting genetic-level features that may be targeted for therapy. Tissue-level features of the tumour microenvironment also represent useful therapeutic targets. Here we investigate the presence of low oxygen tension and sensitivity to NOS inhibition of tumour vasculature as potential tumour-specific features that may be targeted by hypoxic cytotoxins, a class of therapeutics currently under investigation. We have previously demonstrated that tirapazamine (TPZ) mediates central vascular dysfunction in tumours. TPZ is a hypoxic cytotoxin that is also a competitive inhibitor of NOS. Here we further investigated the vascular-targeting activity of TPZ by combining it with NOS inhibitor L-NNA, or with low oxygen content gas breathing. Tumours were analyzed via multiplex immunohistochemical staining that revealed irreversible loss of perfusion and enhanced tumour cell death when TPZ was combined with either low oxygen or a NOS inhibitor. Tumour growth rate was reduced by TPZ + NOS inhibition, and tumours previously resistant to TPZ-mediated vascular dysfunction were sensitized by low oxygen breathing. Additional mapping analysis suggests that tumours with reduced vascular-associated stroma may have greater sensitivity to these effects. These results indicate that poorly oxygenated tumour vessels, also being abnormally organized and with inadequate smooth muscle, may be successfully targeted for significant anti-cancer effects by inhibition of NOS and hypoxia-activated prodrug toxicity. This strategy illustrates a novel use of hypoxia-activated cytotoxic prodrugs as vascular targeting agents, and also represents a novel mechanism for targeting tumour vessels.     

Solution structure by nuclear magnetic resonance of the two lantibiotics 97518 and NAI‐107

Lantibiotics 97518 and NAI‐107, produced by the related genera Planomonospora and Microbispora respectively, are members of a family of nisin‐related compounds. They represent promising compounds to treat infections caused by multiresistant Gram‐positive pathogens. Despite their similar structure and a similar antibacterial spectrum, the two lantibiotics exhibit significant differences in their potency. To gain an insight into the structure–activity relationships, their conformational properties in solution are determined by NMR. After carrying out an NOE analysis of 2D ¹H NMR spectra, high‐resolution 3D structures are determined using molecular dynamics simulations. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.