Overproduction of a Dominant Mutant of the Conserved Era GTPase Inhibits Cell Division in Escherichia coli.

Cell growth and division are coordinated, ensuring homeostasis under any given growth condition, with division occurring as cell mass doubles. The signals and controlling circuit(s) between growth and division are not well understood; however, it is known in Escherichia coli that the essential GTPase Era, which is growth rate regulated, coordinates the two functions and may be a checkpoint regulator of both. We have isolated a mutant of Era that separates its effect on growth and division. When overproduced, the mutant protein Era647 is dominant to wild-type Era and blocks division, causing cells to filament. Multicopy suppressors that prevent the filamentation phenotype of Era647 either increase the expression of FtsZ or decrease the expression of the Era647 protein. Excess Era647 induces complete delocalization of Z rings, providing an explanation for why Era647 induces filamentation, but this effect is probably not due to direct interaction between Era647 and FtsZ. The hypermorphic ftsZ* allele at the native locus can suppress the effects of Era647 overproduction, indicating that extra FtsZ is not required for the suppression, but another hypermorphic allele that accelerates cell division through periplasmic signaling, ftsL*, cannot. Together, these results suggest that Era647 blocks cell division by destabilizing the Z ring.IMPORTANCE All cells need to coordinate their growth and division, and small GTPases that are conserved throughout life play a key role in this regulation. One of these, Era, provides an essential function in the assembly of the 30S ribosomal subunit in Escherichia coli, but its role in regulating E. coli cell division is much less well understood. Here, we characterize a novel dominant negative mutant of Era (Era647) that uncouples these two activities when overproduced; it inhibits cell division by disrupting assembly of the Z ring, without significantly affecting ribosome production. The unique properties of this mutant should help to elucidate how Era regulates cell division and coordinates this process with ribosome biogenesis.

Public awareness and attitudes towards marine protection in the United Kingdom.

Public perception research evaluating awareness and attitudes towards marine protection is limited in the United Kingdom (UK) and worldwide. Given public opinion can help drive policy and affect its successful delivery we conducted nationwide surveys in 2005, 2010 and 2015 to assess public knowledge of UK (England, Scotland and Wales) sea 'health' and management. Respondents from all three surveys were relatively pessimistic about sea 'health', perceiving this as poor-fair and largely in decline. Enthusiasm for marine conservation was high with almost two-thirds of respondents in each survey wanting >40% of UK seas highly protected from fishing and damaging activities. In 2015 there was considerable dissatisfaction with the rate of progress in Marine Conservation Zone designation and over three-quarters of respondents considered dredging and trawling to be inappropriate in protected areas, contrary to management. The UK government and devolved administrations need to better align future conservation and management with public expectations.

Identifying species at extinction risk using global models of anthropogenic impact.

The International Union for Conservation of Nature Red List of Endangered Species employs a robust, standardized approach to assess extinction threat focussed on taxa approaching an end-point in population decline. Used alone, we argue this enforces a reactive approach to conservation. Species not assessed as threatened but which occur predominantly in areas with high levels of anthropogenic impact may require proactive conservation management to prevent loss. We matched distribution and bathymetric range data from the global Red List assessment of 632 species of marine cone snails with human impacts and projected ocean thermal stress and aragonite saturation (a proxy for ocean acidification). Our results show 67 species categorized as 'Least Concern' have 70% or more of their occupancy in places subject to high and very high levels of human impact with 18 highly restricted species (range <100 km(2)) living exclusively in such places. Using a range-rarity scoring method we identified where clusters of endemic species are subject to all three stressors: high human impact, declining aragonite saturation levels and elevated thermal stress. Our approach reinforces Red List threatened status, highlights candidate species for reassessment, contributes important evidential data to minimize data deficiency and identifies regions and species for proactive conservation.

Conus: first comprehensive conservation red list assessment of a marine gastropod mollusc genus.

Marine molluscs represent an estimated 23% of all extant marine taxa, but research into their conservation status has so far failed to reflect this importance, with minimal inclusion on the authoritative Red List of the International Union for the Conservation of Nature (IUCN). We assessed the status of all 632 valid species of the tropical marine gastropod mollusc, Conus (cone snails), using Red List standards and procedures to lay the groundwork for future decadal monitoring, one of the first fully comprehensive global assessments of a marine taxon. Three-quarters (75.6%) of species were not currently considered at risk of extinction owing to their wide distribution and perceived abundance. However, 6.5% were considered threatened with extinction with a further 4.1% near threatened. Data deficiency prevented 13.8% of species from being categorised although they also possess characteristics that signal concern. Where hotspots of endemism occur, most notably in the Eastern Atlantic, 42.9% of the 98 species from that biogeographical region were classified as threatened or near threatened with extinction. All 14 species included in the highest categories of Critically Endangered and Endangered are endemic to either Cape Verde or Senegal, with each of the three Critically Endangered species restricted to single islands in Cape Verde. Threats to all these species are driven by habitat loss and anthropogenic disturbance, in particular from urban pollution, tourism and coastal development. Our findings show that levels of extinction risk to which cone snails are exposed are of a similar magnitude to those seen in many fully assessed terrestrial taxa. The widely held view that marine species are less at risk is not upheld.

Similar modes of polypeptide recognition by export chaperones in flagellar biosynthesis and type III secretion.

Assembly of the bacterial flagellum and type III secretion in pathogenic bacteria require cytosolic export chaperones that interact with mobile components to facilitate their secretion. Although their amino acid sequences are not conserved, the structures of several type III secretion chaperones revealed striking similarities between their folds and modes of substrate recognition. Here, we report the first crystallographic structure of a flagellar export chaperone, Aquifex aeolicus FliS. FliS adopts a novel fold that is clearly distinct from those of the type III secretion chaperones, indicating that they do not share a common evolutionary origin. However, the structure of FliS in complex with a fragment of FliC (flagellin) reveals that, like the type III secretion chaperones, flagellar export chaperones bind their target proteins in extended conformation and suggests that this mode of recognition may be widely used in bacteria.

Structural basis for the substrate specificity of tobacco etch virus protease.

Because of its stringent sequence specificity, the 3C-type protease from tobacco etch virus (TEV) is frequently used to remove affinity tags from recombinant proteins. It is unclear, however, exactly how TEV protease recognizes its substrates with such high selectivity. The crystal structures of two TEV protease mutants, inactive C151A and autolysis-resistant S219D, have now been solved at 2.2- and 1.8-A resolution as complexes with a substrate and product peptide, respectively. The enzyme does not appear to have been perturbed by the mutations in either structure, and the modes of binding of the product and substrate are virtually identical. Analysis of the protein-ligand interactions helps to delineate the structural determinants of substrate specificity and provides guidance for reengineering the enzyme to further improve its utility for biotechnological applications.

The global regulator RNase III modulates translation repression by the transcription elongation factor N.

Efficient expression of most bacteriophage lambda early genes depends upon the formation of an antiterminating transcription complex to overcome transcription terminators in the early operons, p(L) and p(R). Formation of this complex requires the phage-encoded protein N, the first gene product expressed from the p(L) operon. The N leader RNA contains, in this order: the NUTL site, an RNase III-sensitive hairpin and the N ribosome-binding site. N bound to NUTL RNA is part of both the antitermination complex and an autoregulatory complex that represses the translation of the N gene. In this study, we show that cleavage of the N leader by RNase III does not inhibit antitermination but prevents N-mediated translation repression of N gene expression. In fact, by preventing N autoregulation, RNase III activates N gene translation at least 200-fold. N-mediated translation repression is extremely sensitive to growth rate, reflecting the growth rate regulation of RNase III expression itself. Given N protein's critical role in lambda development, the level of RNase III activity therefore serves as an important sensor of physiological conditions for the bacteriophage.