Cold adaption of enzymes: Structural comparison between salmon and bovine trypsins

The crystal structure of an anionic form of salmon trypsin has been determined at 1.82 Å resolution. We report the first structure of a trypsin from a phoikilothermic organism in a detailed comparison to mammalian trypsins in order to look for structural rationalizations for the cold-adaption features of salmon trypsin. This form of salmon trypsin (T II) comprises 222 residues, and is homologous to bovine trypsin (BT) in about 65% of the primary structure. The tertiary structures are similar, with an overall displacement in main chain atomic positions between salmon trypsin and various crystal structures of bovine trypsin of about 0.8 Å. Intramolecular hydrogen bonds and hydrophobic interactions are compared and discussed in order to estimate possible differences in molecular flexibility which might explain the higher catalytic efficiency and lower thermostability of salmon trypsin compared to bovine trypsin. No overall differences in intramolecular interactions are detected between the two structures, but there are differences in certain regions of the structures which may explain some of the observed differences in physical properties. The distribution of charged residues is different in the two trypsins, and the impact this might have on substrate affinity has been discussed. © 1994 Wiley-Liss, Inc.     

A phytoecological study of the mire Northern Kisselbergmosen, SE Norway. II. Identification of gradients by detrended (canonical) correspondence analysis

The vegetation of a poor mire is sampled by two procedures; 800 randomly placed sample plots made up the R data set, 765 subjectively selected plots in 153 sample plot series made up the S data set. DCA ordination and constrained ordination by DCCA of the data sets and subsets showed the existence of three coenoclines in the material: (1) the coenocline along the mire expanse: low to high median depth to the water table—mire margin gradient, (2) the poor-rich coenocline, dependent on a complex-gradient in substrate chemistry, and (3) a coenocline attributed to variation in peat productivity. Thus the assumption of Fennoscandian mire scientists embedded in numerous systems for classifying mire vegetation, that three gradients are the most important in the mire ecosystem, is partly confirmed. In the investigated area, two of the gradients normally considered make up one complex coenocline (1), and a fourth coenocline (3) has to be added. The effects of sampling techniques on correlations between coenoclines and on ordination results are discussed, and an improved sampling technique is suggested. The major faults of DCA: (1) the tongue effect, and (2) the instability, are described and discussed. It is concluded that if due attention is taken to reveal effects of the faults of the method, DCA is among the best ordination methods currently available.     

Regional variation in SE Fennoscandian mire vegetation

The distribution in bogs is outlined for all species occurring in bogs only in part of their SE Fennoscandian area. The patterns displayed by these species are diverse, and different explanations are applicable to different patterns. Regional variation in SE Fennoscandian bog and extremely poor fen vegetation is described, based on all available published material. Carpets, lawns, and hummocks are considered separately. Four regional vegetational gradients are identified: (1) W-E, (2) S-N, (3) SW-NE, and (4) NW-SE. These are related to different underlying climatic gradients: (1) humidity (precipitation surplus), (2) temperature, (3) and (4) combinations of humidity and temperature. Effects of climatic gradients on the ground water regime are outlined. The decisive factor for the SW-NE gradient is probably frequency of ground water table fluctuations, the NW-SE gradient is likely to be caused by differences in water supply and ground water flow rates. The main gradient of carpets is S-N (SE-NW), of lawns SW-NE (W-E), and of hummocks partly SW-NE, partly S-N. The effects of the underlying ecological factors on the different plant groups are discussed in order to explain the patterns of regional variation in vegetation.     

Conversion of cephalosporin-c into 7-phenoxy-acetamido-cephalosporanic acid by acyltransferase of mutants of Penicillium chrysogenum

Summary We have tested the acyl-transferase of penicillin producing strains and penicillin-less mutants of Penicillium chrysogenum for their ability to exchange the d--aminoadipic acid side chain of cephalosporin-C with phenoxyacetic acid. We found the reaction in both types of strains.     

High‐density areas for harbor porpoises (Phocoena phocoena) identified by satellite tracking

The population status of harbor porpoises has been of concern for several years, and the establishment of Marine Protected Areas (MPAs) has been suggested as a method to protect the harbor porpoise (Phocoena phocoena, Linneaus 1758) and other small cetaceans. In order to designate MPAs, high‐density areas for the species must be identified. Spatial distribution of small cetaceans is usually assessed from ship or aerial surveys. As a potentially more accurate alternative, this study examined the movements and area preferences of 64 harbor porpoises, satellite tagged between 1997 and 2007, in order to determine the distribution in the North Sea, the western Baltic, and the waters in between. Results show that harbor porpoises are not evenly distributed, but congregate in nine high‐density areas within the study area. Several of these areas are subject to significant seasonal variation. The study found no differences in the home range size of males and females, but immature harbor porpoises have larger home ranges than mature porpoises. The use of satellite telemetry for identifying areas of high harbor porpoise density can be of key importance when designating MPAs.     

Multi‐factor climate change effects on insect herbivore performance

The impact of climate change on herbivorous insects can have far‐reaching consequences for ecosystem processes. However, experiments investigating the combined effects of multiple climate change drivers on herbivorous insects are scarce. We independently manipulated three climate change drivers (CO₂, warming, drought) in a Danish heathland ecosystem. The experiment was established in 2005 as a full factorial split‐plot with 6 blocks × 2 levels of CO₂ × 2 levels of warming × 2 levels of drought = 48 plots. In 2008, we exposed 432 larvae (n = 9 per plot) of the heather beetle (Lochmaea suturalis Thomson ), an important herbivore on heather, to ambient versus elevated drought, temperature, and CO₂ (plus all combinations) for 5 weeks. Larval weight and survival were highest under ambient conditions and decreased significantly with the number of climate change drivers. Weight was lowest under the drought treatment, and there was a three‐way interaction between time, CO₂, and drought. Survival was lowest when drought, warming, and elevated CO₂ were combined. Effects of climate change drivers depended on other co‐acting factors and were mediated by changes in plant secondary compounds, nitrogen, and water content. Overall, drought was the most important factor for this insect herbivore. Our study shows that weight and survival of insect herbivores may decline under future climate. The complexity of insect herbivore responses increases with the number of combined climate change drivers.     

Inhibition of NF-κB signaling interferes with phorbol ester-induced growth arrest of keratinocytes in a TNFR1-independent manner

A skin-specific block in NF-κB signaling leads to hyperproliferation of the keratinocytes, inflammation, and spontaneous development of squamous cell carcinoma (SCC). Here we show that an inhibition of NF-κB signaling in keratinocytes, via the expression of the super-repressor/ degradation-resistant form of the IκBα protein (IκBαDN), interferes with the growth arrest induced by the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA). The IκBαDN cells are able to overcome the TPA-induced cell cycle block. Although SCC development as well as hyperproliferation due to IκBαDN expression in keratinocytes is known to require TNFR1 signaling, the effect of IκBαDN on phorbol ester signaling is downstream/independent of TNFR1. These data thus identify an interaction between IκBαDN and the tumor promoter TPA in the growth regulation of keratinocytes. The proposed mechanism is also likely to be significant in the process of cancer development due to NF-κB inhibition.