Crystal structures of the two major aggrecan degrading enzymes, ADAMTS4 and ADAMTS5

Aggrecanases are now believed to be the principal proteinases responsible for aggrecan degradation in osteoarthritis. Given their potential as a drug target, we solved crystal structures of the two most active human aggrecanase isoforms, ADAMTS4 and ADAMTS5, each in complex with bound inhibitor and one wherein the enzyme is in apo form. These structures show that the unliganded and inhibitor-bound enzymes exhibit two essentially different catalytic-site configurations: an autoinhibited, nonbinding, closed form and an open, binding form. On this basis, we propose that mature aggrecanases exist as an ensemble of at least two isomers, only one of which is proteolytically active.     

The nature of Staphylococcus aureus MurA and MurZ and approaches for detection of peptidoglycan biosynthesis inhibitors

Staphylococcus aureus and a number of other Gram-positive organisms harbour two genes ( murA and murZ ) encoding UDP- N -acetylglucosamine enolpyruvyl transferase activity for catalysing the first committed step of peptidoglycan biosynthesis. We independently inactivated murA and murZ in S. aureus and established that either can sustain viability. Purification and characterization of the MurA and MurZ enzymes indicated that they are biochemically similar in vitro , consistent with similar overall structures predicted for the isozymes by molecular modelling. Nevertheless, MurA appears to be the primary enzyme utilized in the staphylococcal cell. Accordingly, murA expression was approximately five times greater than murZ expression during exponential growth, and the peptidoglycan content of S. aureus was reduced by approximately 25% following inactivation of murA , but remained almost unchanged following inactivation of murZ . Despite low level expression during normal growth, murZ expression was strongly induced (up to sixfold) following exposure to inhibitors of peptidoglycan biosynthesis, which was not observed for murA . Strains generated in this study were validated as potential tools for identifying novel anti-staphylococcal agents targeting peptidoglycan biosynthesis using known inhibitors of the pathway.     

Molecular Phylogenetics of the Genus Neoconocephalus (Orthoptera,Tettigoniidae) and the Evolution of Temperate Life Histories

Background

The katydid genus Neoconocephalus (25+ species) has a prominent acoustic communication system and occurs in large parts of the Neotropics and Nearctic. This group has been subject of numerous behavioral, physiological, and evolutionary studies of its acoustic communication system. Two distinct life histories occur in this group: The tropical life history incorporates multiple generations/year and direct egg development without environmental triggers. Temperate life history is characterized by overwintering in the egg stage, cold trigger of egg development, and one generation/year. This study reconstructs the phylogenetic relationships within the genus to (1) determine the evolutionary history of the temperate life history, and (2) to support comparative studies of evolutionary and physiological problems in this genus.

Methodology/Principal Findings

We used Amplified Fragment Length Polymorphisms (AFLP), and sequences of two nuclear loci and one mitochondrial locus to reconstruct phylogenetic relationships. The analysis included 17 ingroup and two outgroup species. AFLP and mitochondrial data provided resolution at the species level while the two nuclear loci revealed only deeper nodes. The data sets were combined in a super-matrix to estimate a total evidence tree. Seven of the temperate species form a monophyletic group; however, three more temperate species were placed as siblings of tropical species.

Conclusions/Significance

Our analyses support the reliability of the current taxonomic treatment of the Neoconocephalus fauna of Caribbean, Central, and North America. Ancestral state reconstruction of life history traits was not conclusive, however at least four transitions between life histories occurred among our sample of species. The proposed phylogeny will strengthen conclusions from comparative work in this group.     

Conservation of oceanic island floras: Present and future global challenges

Current threats to the planet's biodiversity are unprecedented, and they particularly imperil insular floras. In this investigation, we use the threat factors identified by the Millennium Ecosystem Assessment as the main drivers of biodiversity loss on islands to define and rank 13 current, continuing threats to the plant diversity of nine focal archipelagos where volcanic origin (or in the Seychelles a prolonged isolation after a continental origin) has produced a high degree of endemicity and fragility in the face of habitat alteration. We also conduct a global endangerment assessment based on the numbers of insular endemic plants in the endangered (EN) and critically endangered (CR) IUCN categories for 53 island groups with an estimated 9951 endemic plant species, providing a representative sample of the world's insular systems and their floristic richness. Our analyses indicate that isolation does not significantly influence endangerment, but plant endemics from very small islands are more often critically endangered. We estimate that between 3500 and 6800 of the estimated 70,000 insular endemic plant species worldwide might be highly threatened (CR+EN) and between ca. 2000 and 2800 of them in critical danger of extinction (CR). Based on these analyses, and on a worldwide literature review of the biological threat factors considered, we identify challenging questions for conservation research, asking (i) what are the most urgent priorities for the conservation of insular species and floras, and (ii) with the knowledge and assets available, how can we improve the impact of conservation science and practice on the preservation of island biodiversity? Our analysis indicates that the synergistic action of many threat factors can induce major ecological disturbances, leading to multiple extinctions. We review weaknesses and strengths in conservation research and management in the nine focal archipelagos, and highlight the urgent need for conservation scientists to share knowledge and expertise, identify and discuss common challenges, and formulate multi-disciplinary conservation objectives for insular plant endemics worldwide. To our knowledge, this is the most up-to-date and comprehensive survey yet to review the threat factors to native plants on oceanic islands and define priority research questions.     

Discovery of a potent phenolic N1-benzylidene-pyridinecarboxamidrazone selective against Gram-positive bacteria

As part of a study into antimycobacterial compounds a set of phenolic N1-benzylidene-pyridinecarboxamidrazones was prepared and evaluated. This report describes the unexpected discovery of a potent compound with a pronounced selectivity for Gram-positive bacteria over Gram-negative micro-organisms. In addition, this compound is active against various drug-resistant Gram-positive bacteria.