Enzyme Sequence and Its Relationship to Hyperbaric Stability of Artificial and Natural Fish Lactate Dehydrogenases

The cDNAs of lactate dehydrogenase b (LDH-b) from both deep-sea and shallow living fish species, Corphaenoides armatus and Gadus morhua respectively, have been isolated, sequenced and their encoded products overproduced as recombinant enzymes in E. coli. The proteins were characterised in terms of their kinetic and physical properties and their ability to withstand high pressures. Although the two proteins are very similar in terms of their primary structure, only 21 differences at the amino acid level exist between them, the enzyme from the deep-sea species has a significantly increased tolerance to pressure and a higher thermostability. It was possible to investigate whether the changes in the N-terminal or C-terminal regions played a greater role in barophilic adaptation by the construction of two chimeric enzymes by use of a common restriction site within the cDNAs. One of these hybrids was found to have even greater pressure stability than the recombinant enzyme from the deep-living fish species. It was possible to conclude that the major adaptive changes to pressure tolerance must be located in the N-terminal region of the protein. The types of changes that are found and their spatial location within the protein structure are discussed. An analysis of the kinetic parameters of the enzymes suggests that there is clearly a trade off between Km and kcat values, which likely reflects the necessity of the deep-sea enzyme to operate at low temperatures

A1 Adenosine Receptor Modulation of Adenylyl Cyclase of a Deep-living Teleost Fish, Antimora rostrata

Volume: 178Start Page: 65End Page: 7

Hydrostatic Pressure Alters the Time Course of GTP[S] Binding to G Proteins in Brain Membranes from Two Congeneric Marine Fishes

Volume: 197Start Page: 388End Page: 39

The effects of the deep-sea environment on transmembrane signaling

Membrane-associated processes may be particularly susceptible to perturbation by the high hydrostatic pressures and low temperatures of the deep ocean. Transmembrane signaling by guanyl nucleotide binding protein (G protein) coupled receptors (GPCRs) is affected at a number of steps: (1) agonist activation of the GPCR; (2) the interaction of the receptor with the heterotrimeric G protein; (3) the G protein GTPase cycle; and (4) the activation and function of the effector element, adenylyl cyclase. The effects of low temperature and high hydrostatic pressures on the A(1) adenosine receptor-inhibitory G protein (G(i))-adenylyl cyclase signaling complex were examined in teleost fishes from three families, Scorpaenidae, Macrouridae and Moridae. In a comparison of teleost fishes, rat and chicken, species with body temperatures from 1 to 40 degrees C, at atmospheric pressure, A(1) adenosine receptor agonist binding is conserved at the body temperature of the species. In the marine teleost fishes examined, increased pressure decreases agonist efficacy. There are differences among species in the effects of increased hydrostatic pressure on G protein interactions with receptors, GTP binding to G protein alpha subunits and the intrinsic GTPase activity of alpha subunits. Adenylyl cyclase activity and modulation are affected by increased pressure in all the species examined, except Antimora rostrata which was unaffected by pressure changes. At pressures approximating those which the species experience in situ adenylyl cyclase activity retains its sensitivity to modulators. To understand the physiological consequences of impaired cell signaling several prototypical human diseases are discussed

Differential Susceptibility of Guanine Nucleotide-binding Proteins to Pertussis Toxin-catalyzed ADP-ribosylation in Brain Membranes of Two Congeneric Marine Fishes

Volume: 185Start Page: 346End Page: 35

Formation of Fluid Inclusions during Heat Treatment of Barremo-Bedoulian Flint: Archaeometric Implications

International audienc

Arsenic removal with zero-valent iron filters in Burkina Faso:Field and laboratory insights

Groundwater contaminated with geogenic arsenic (As) is frequently used as drinking water in Burkina Faso, despite adverse health effects. This study focused on testing low-cost filter systems based on zero-valent iron (ZVI), which have not yet been explored in West Africa for As removal. The active ZVI bed was constructed using small-sized iron nails, embedded between sand layers. Household filters were tested for nine months in a remote village relying on tube well water with As concentrations of 400–1350 μg/L. Daily filtered volumes were 40–60 L, with flow rates of ~10 L/h. In parallel, downscaled laboratory filter columns were run to find the best set-up for optimal As removal, with special attention given to the influence of input pH, flow rate and water/nail contact time. Arsenic removal efficiencies in the field were 60–80% in the first six months of operation. The laboratory experiments revealed that trapped air in the nail layer greatly lowered As removal due to preferential flow and decreased water/nail contact time. Measures taken to avoid trapped air led to a partial improvement in the field filters, but effluent As remained &gt;50 μg/L. Similar structural modifications were however very successful in the laboratory columns, where As removal efficiencies were consistently &gt;95% and effluent concentrations frequently &lt;10 μg/L, despite inflow As &gt;1000 μg/L. A constantly saturated nail bed and careful flow control is necessary for optimal As removal. Slow flow and longer pauses between filtrations are important for sufficient contact times and for transformation of brown amorphous Fe-hydroxides to dense magnetite with incorporated As(V). This preliminary study has shown that nail-based filters have the potential to achieve As removal &gt;90% in a field context if conditions (filter bed saturation, flow rate, pauses between filtrations) are well controlled.</p