A New Mode of Dimerization of Allosteric Enzymes with ACT Domains Revealed by the Crystal Structure of the Aspartate Kinase from Cyanobacteria

Aspartate kinases (AKs) can be divided in two subhomology divisions, AKα and AKβ, depending on the presence of an extra sequence of about 60 amino acids, which is found only in the N-terminus of all AKα's. To date, the structures of AKα failed to provide a role for this additional N-terminal sequence. In this study, the structure of the AKβ from the Cyanobacteria Synechocystis reveals that this supplementary sequence is linked to the dimerization mode of AKs. Its absence in AKβ leads to the dimerization by the catalytic domain instead of involving the ACT domains [Pfam 01842; small regulatory domains initially found in AK, chorismate mutase and TyrA (prephenate dehydrogenase)] as observed in AKα. Thus, the structural analysis of the Synechocystis AKβ revealed a dimer with a novel architecture. The four ACT domains of each monomer interact together and do not make any contact with those of the second monomer. The enzyme is inhibited synergistically by threonine and lysine with the binding of threonine first. The interaction between ACT1 and ACT4 or between ACT2 and ACT3 generates a threonine binding site and a lysine binding site at each interface, making a total of eight regulatory sites per dimer and allowing a fine-tuning of the AK activity by the end products, threonine and lysine.     

Weak meiofaunal trophic linkages in Crangon crangon and Carcinus maenus

To document the relative importance of meiofauna as prey for juvenile Crangon crangon and Carcinus maenus, short interval (1.5-2 h) collections were made in the muddy Lynher Estuary (Plymouth, Great Britain) and in the sandy-bottom Ythan Estuary (Aberdeenshire, Scotland) in 1990. Gut passage times of Crangon fed flaked fish food and fluorescent tracer in the laboratory at 13 °C ranged from 4 to 20 h. Wild shrimp exhibited feeding periodicity, with guts fullest during high tide in both locations. Visual and immunological gut contents analyses revealed that meiofaunal nematodes and harpacticoid copepods were present only in recently settled shrimp from 8 to 12 mm total length on muddy bottoms. Larger shrimp collectively consumed up to 33 different macrobenthic prey types. Shrimp were fullest at night (mean gut contents weight = 8% wet body weight, Lynher) or at dawn (6%, Ythan). The Lynher Carcinus gut contents—from animals 8 to 30 mm carapace width, examined visually only—contained mostly fluids, green benthic algae, sediment particles, and masses of unidentifiable prey remains plus digestion-resistant hard parts visually identifiable as macrobenthic in origin. None of the 203 crabs examined from the 24-h collection contained meiofaunal prey. Crangon shrimp probably eat meiofaunal prey for only a brief period of time after their initial settlement to the bottom. Evidence for significant top-down impacts on meiofauna from these two abundant shallow-water predators was weak. More trophic studies are needed on newly settled epibenthic predators to test the hypothesis that biological control of shallow-water meiofauna is important.     

Investigation of the binding of inorganic complexes to blue copper proteins by 1H nmr spectroscopy,I. The interaction between the [Cr(phen)3]3+ and [Cr(CN)6]3− ions and the copper(I) form of parsley plastocyanin

The effects of the addition of [Cr(phen)₃](ClO₄)₃ and K₃[Cr(CN)₆] on the ¹H nmr spectrum of the copper(I) form of parsley plastocyanin are described. It is concluded that the ions [Cr(phen)₃]³⁺ and [Cr(CN)₆]^3? bind to different parts of the protein.     

The effects of age,sex, and zinc status on the accumulation of (copper,zinc)-metallothionein in rat kidneys

A study has been made of the distribution of copper in the kidneys of growing rats. Renal copper concentrations increased steadily with age and were greater in female than in male animals. Most of the copper was present as (copper, zinc)-metallothionein and two forms of this protein were isolated and characterized from the kidneys of mature female rats. That copper metabolism in kidneys is subject to hormonal influence was indicated by a reduction in the concentrations of copper and (copper, zinc)-metallothionein in ovariectomized rats and by an increase in their concentrations after the administration of progesterone. Concentrations of renal (copper, zinc)-metallothionein were less in zinc-deficient than in zinc-adequate rats during pregnancy and after progesterone administration.     

Conservation regulation: a backward step for biodiversity?

An analysis, particularly from the UK and European Community perspectives, of the way in which the law dealing with the conservation of species and habitats has the potential effect, in some cases, of frustrating the comprehensive preservation of biological diversity. It is proposed that this state of affairs may have come about through the emphasis of one species to the detriment of others or through the failure to address comprehensive inter-species and habitat relationships. One of the propositions is that the application of protection to specific species, through conservation and wild animal welfare provisions, has been implemented in an arbitrary manner in the context of biodiversity preservation or in terms of an animal's level of sentiency or position on the phylogenetic scale. Another proposition is that the law has failed to protect and preserve the 'commonplace' in biodiversity and thus risks losing key components of ecosystems. Finally, the analysis examines the way in which traditional practices such as hunting with hounds may contribute to or frustrate biodiversity preservation.     

High cancer mortality rates in the elderly in the UK

Introduction: Cancer is largely a disease of older individuals. We compared UK cancer mortality rates with those for other countries to assess progress. Methods: Death details were obtained from the WHO Mortality Database for the UK, the USA and 11 European countries. Mortality rates were calculated for the age groups 55–64, 65–74, 75–84 and ≥85 years. Trends between 1995–97 and 2003–05 were determined. The number of excess cancer deaths in the UK was calculated by applying the age-specific mortality rates observed in other regions to the UK. Results: For all cancers combined, UK rates for 2003–05 in those aged ≥75 years were 11–31% higher than in other regions. From 1995–97 to 2003–05, UK rates decreased by 16–17% in those aged <75 years, but increased by 2% in those ≥85 years compared with decreases of 4–16% for the other geographic areas. More than 14,000 cancer deaths in the UK in those aged ≥75 years would be avoided each year if UK mortality rates were identical to those in the USA. Conclusion: The UK is making poor progress in controlling cancer in older age groups. The gap in mortality rates between the UK and other countries and between old and young in the UK is widening.     

A comparison of deoxynivalenol intake and urinary deoxynivalenol in UK adults

The relationship between deoxynivalenol (DON) intake and first morning urinary DON was examined in UK adults to validate the latter as a biomarker of human exposure. DON was assessed in first morning samples collected during a period of normal diet, a wheat-restriction intervention diet, and partial wheat-restriction intervention in which bread was allowed. During the partial intervention duplicate bread portions were collected for DON analysis. During the normal diet, partial intervention and full intervention, urinary DON was detected in 198/210 (geometric mean 10.1?ng DON mg^?1 creatinine, 95% confidence interval (CI) 8.6–11.6?ng mg^?1; range nd–70.7?ng mg^?1), in 94/98 (5.9?ng mg^?1, 95% CI 4.8–7.0?ng mg^?1; range nd–28.4?ng mg^?1), and 17/40 (0.5?ng mg^?1, 95% CI 0.3–0.7?ng mg^?1; range nd–3.3?ng mg^?1) volunteers, respectively. A strong correlation between DON intake and the urinary biomarker was observed (p <0.001, adjusted r²?=?0.83) in models adjusting for age, sex and body mass index. These data demonstrate a quantitative correlation between DON exposure and urinary DON, and serve to validate the use of urinary DON as an exposure biomarker.