Cl Anion-Dependent Mg-ATPase

We studied, in the rat brain, the synaptosomal and microsomal membrane fractions of Cl− ion-activated, Mg2+-dependent ATPase, satisfying the necessary kinetic peculiarities of transport ATPases, by a novel method of kinetic analysis of the multisite enzyme systems: (1) the [Mg-ATP] complex constitutes the substrate of the enzymic reaction; (2) the V = f(Cl−) dependence-reflecting curve is bell-shaped; (3) substrate dependence, V = f(S), curves at a constant concentration of free ligands (Mgf, ATPf, Cl−); (4) as known from the literature, in the process of reaction a phosphorylated intermediate is formed (Gerencser, Crit Rev Biochem Mol Biol 31:303–337, 1996). We report on the Cl-ATPase molecular mechanism and its place in the “P-type ATPase” classification

Bioinformatic Characterization of P-Type ATPases Encoded Within the Fully Sequenced Genomes of 26 Eukaryotes

P-type ATPases play essential roles in numerous processes, which in humans include nerve impulse propagation, relaxation of muscle fibers, secretion and absorption in the kidney, acidification of the stomach and nutrient absorption in the intestine. Published evidence suggests that uncharacterized families of P-type ATPases with novel specificities exist. In this study, the fully sequenced genomes of 26 eukaryotes, including animals, plants, fungi and unicellular eukaryotes, were analyzed for P-type ATPases. We report the organismal distributions, phylogenetic relationships, probable topologies and conserved motifs of nine functionally characterized families and 13 uncharacterized families of these enzyme transporters. We have classified these proteins according to the conventions of the functional and phylogenetic IUBMB-approved transporter classification system (www.tcdb.org, Saier et al. in Nucleic Acids Res 34:181–186, 2006; Nucleic Acids Res 37:274–278, 2009)

Coral Uptake of Inorganic Phosphorus and Nitrogen Negatively Affected by Simultaneous Changes in Temperature and pH

The effects of ocean acidification and elevated seawater temperature on coral calcification and photosynthesis have been extensively investigated over the last two decades, whereas they are still unknown on nutrient uptake, despite their importance for coral energetics. We therefore studied the separate and combined impacts of increases in temperature and pCO2 on phosphate, ammonium, and nitrate uptake rates by the scleractinian coral S. pistillata. Three experiments were performed, during 10 days i) at three pHT conditions (8.1, 7.8, and 7.5) and normal temperature (26°C), ii) at three temperature conditions (26°, 29°C, and 33°C) and normal pHT (8.1), and iii) at three pHT conditions (8.1, 7.8, and 7.5) and elevated temperature (33°C). After 10 days of incubation, corals had not bleached, as protein, chlorophyll, and zooxanthellae contents were the same in all treatments. However, photosynthetic rates significantly decreased at 33°C, and were further reduced for the pHT 7.5. The photosynthetic efficiency of PSII was only decreased by elevated temperature. Nutrient uptake rates were not affected by a change in pH alone. Conversely, elevated temperature (33°C) alone induced an increase in phosphate uptake but a severe decrease in nitrate and ammonium uptake rates, even leading to a release of nitrogen into seawater. Combination of high temperature (33°C) and low pHT (7.5) resulted in a significant decrease in phosphate and nitrate uptake rates compared to control corals (26°C, pHT = 8.1). These results indicate that both inorganic nitrogen and phosphorus metabolism may be negatively affected by the cumulative effects of ocean warming and acidification

Intestinal glucose transport in carnivorous and herbivorous marine fishes

The influx and transepithelial movements of glucose and their effects on the electrophysiology and Na transport in upper and lower intestines of the herbivorous surgeonfish, Acanthurus mata , and carnivorous eel, Gymnothorax undulatus , were measured. The K t G and J max G of glucose influx into the tissues were higher in the surgeonfish upper intestine than in the surgeonfish lower intestine or in both segments of the eel intestine. A prominent diffusion-like transport component was also measured in all four segments during influx experiments. Net transepithelial glucose fluxes (0.05 mM) were greater in eel intestine than in those of the surgeonfish largely due to an apparent lower apical membrane permeability of the former coincident with reduced backflux of glucose from epithelium to lumen. All four stripped intestinal segments exhibited non-significant (from zero; P >0.05) or small, serosa-negative transepithelial potential differences (-0.1 to -2.2 mV), and low transepithelial resistances (40–88 O cm -2 ). Each tissue displayed significant ( P P >0.05) change the transepithelial resistance, but did induce a significant ( P J net Na with added luminal glucose, these increased net cation fluxes were not quite significant ( P >0.05). It is concluded that coupled Na-glucose transport occurs in these tissues, but that metabolic enhancement of unrelated current-generating mechanisms also takes place and may modify depolarizing effects of organic solute transfer