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Highlights • 76% of the interactions between reduced seawater pH and increasing copper concentrations were antagonistic. • The interaction of stressors did not result in deleterious effects on endosymbiont´s photosynthetic metabolism or Ca-ATPase activity. • Low copper concentrations had a consistent positive effect on Ca-ATPase activity in corals facing reduced seawater pH conditions. • Potential deleterious effects on the acid-base balance of corals were intensified by the combination of stressors. • Toxic effects of copper in future ocean acidification scenarios can be less severe than previously suggested. Abstract Coral reefs are threatened by global and local impacts, such as ocean acidification (OA) and metal contamination. Toxicity of metals, such as copper (Cu), is expected to be enhanced with OA. However, the interaction between these environmental stressors is still poorly evaluated. In the present study, the interactive effects of seawater acidification and increasing Cu concentrations were evaluated in a zooxanthellate scleractinian coral (Mussismilia harttii), using biochemical biomarkers involved in the coral calcification process and the photosynthetic metabolism of endosymbionts. Corals were kept under control conditions (no seawater acidification and no Cu addition in seawater) or exposed to combined treatments of reduced seawater pH (8.1, 7.8, 7.5 and 7.2) and environmentally relevant concentrations of dissolved Cu (measured: 1.0, 1.6, 2.3 and 3.2 μg/L) in a mesocosm system. After 15- and 35-days exposure, corals were analyzed for photochemical efficiency (F v/ F m), chlorophyll a content, Ca-ATPase and carbonic anhydrase (CA) activity. Results showed that 76% of the interactions between reduced seawater pH and increasing Cu concentrations were antagonistic. Only 24% of these interactions were additive or synergistic. In general, the combination of stressors had no significant deleterious effects in the photosynthetic metabolism of endosymbionts or Ca-ATPase activity. In fact, the lowest dissolved Cu concentration tested had a consistent positive effect on Ca-ATPase activity in corals facing any of the reduced seawater pH conditions tested. In turn, potentially deleterious effects on acid-base balance in M. harttii , associated with changes in CA activity, were intensified by the combination of stressors. Findings reported here indicate that Cu toxicity in future OA scenarios can be less severe than previously suggested in this coral holobiont. [ABSTRACT FROM AUTHOR]

We investigated the effect of chitooligosaccharides on the denaturation of weever (Lateolabrax japonicus) myofibrillar protein during frozen storage at −18°C for 90 days. Chitooligosaccharides (2.5–10g dry weight) were added to 100g of myofibrillar protein, and the changes in the Ca-adenylpyrophosphatase (ATPase) activity, unfrozen water content, solubility, and sulfhydryl content of the myofibrillar protein were examined during frozen storage. We observed that the Ca-ATPase activity and solubility of the myofibrillar protein decreased gradually during frozen storage at −18°C following the addition of chitooligosaccharides. In contrast, the Ca-ATPase activity and solubility of the myofibrillar protein of the control group decreased markedly during the first 45 days of storage and then further decreased gradually for up to 90 days of storage, indicating a biphasic denaturation pattern. The addition of chitooligosaccharides resulted in a significant increase in unfrozen water and sulfhydryl contents of the myofibrillar protein of the treatment group compared with that of the control group (p <0.05) during frozen storage at −18°C. [ABSTRACT FROM AUTHOR]

Abstract: Objective: The aim of this work was to isolate the sarcoplasmic reticulum (SR) Ca-ATPase from rabbit temporalis muscle and to determine the optimal conditions for calcium transport and enzymatic activity. Design: SR vesicles were isolated from rabbit temporalis muscle by differential centrifugation, the protein composition analyzed by electrophoresis and compared to fast-twitch muscle membrane suspensions. ELISA was used to determine the sarcoendoplasmic reticulum Ca-ATPase (SERCA) isoform. Ca-ATPase activity was determined by a colorimetric method. Calcium-binding to the Ca-ATPase, calcium uptake, calcium efflux and phosphorylation by Pi were determined with radioisotopic techniques. Results: Sixty five percent of the total protein concentration of SR membranes suspensions from rabbit temporalis corresponded to SERCA. Of the total SERCA protein, 64% was SERCA 2, 35% was SERCA 1 and less than 1% was SERCA 3. The optimal conditions of the SERCA isolated from rabbit temporalis muscle were: pH 7.2, 5μM Ca2+, 100μM EGTA, 90μM Mg2+, 3mM ATP and 100mM KCl and did not differ from fast-twitch skeletal muscle. The temporalis maximal calcium uptake and Ca-ATPase activity were lower but the sensitivity to the specific Ca-ATPase inhibitor thapsigargin was higher. Calcium-binding to the enzyme and calcium efflux were similar while the phosphorylation of the enzyme by Pi was lower. Conclusion: The lower enzymatic activity and calcium transport capability of the Ca-ATPase isolated from rabbit temporalis, and the higher sensitivity to inhibitory drugs are consistent with the presence of a substantial proportion of SERCA 2, which can be expected in other rabbit masticatory muscles. [Copyright &y& Elsevier]

Abstract: Protein hydrolysates (SH, TH) were prepared from eel head by enzymatic treatment using protease. The eel head hydrolysates were used as a natural food preservative by adding to grass carp surimi at the 10% ranging. We compared the effect of protein hydrolysates of eel head with traditional antifreeze on the denatration, gel strength and contents of the salt soluble protein in grass carp surimi during frozen storage at -20°C for 80 days. The addition of eel head hydrolysate markedly decreased the activation rate of the Ca-ATPase. The contents of the salt soluble protein in the grass carp surimi containing eel head hydrolysates were higher than those without eel head hydrolysates (control).Therefore, the gel strength of grass carp surimi media with eel head hydrolysate lower than the others. The result suggests that eel head hydrolysate could suppress the denaturation of grass carp surimi during frozen storage. [Copyright &y& Elsevier]

Abstract: A Dutch Improved Red and White cross-breed heifer calf was evaluated for a muscular disorder resulting in exercise induced muscle stiffness. Clinical findings included generalized exercise-induced muscle spasms with normal response to muscle percussion. Electromyography showed no myotonic discharges, thus ruling out myotonia. Whereas histological examination of muscle tissue was unremarkable, Ca2+-ATPase activity of sarcoplasmatic reticulum membranes (SERCA1) was markedly decreased compared to control animals. Mutation analysis revealed the presence of a missense mutation in the ATP2A1 gene encoding the SERCA1 protein (p.Arg559Cys). The present case presents similarities to human Brody’s disease, but also to pseudomyotonia and congenital muscular dystonia previously described in different cattle breeds. [Copyright &y& Elsevier]

Abstract: The thermal denaturation process of myosin in oxidized chicken myofibrils was investigated. Exposures of myofibrils to hydroxyl radical-generation systems (HRGS) resulted in an enhanced susceptibility of myosin to thermal inactivation of Ca-ATPase and a loss of salt solubility. The chymotryptic production of subfragment-1 (S-1) from myosin in oxidized myofibrils decreased more rapidly than that in un-oxidized myofibrils upon heating, which paralleled the Ca-ATPase decay. However, the heat-induced decrease in chymotryptic production of rod from myosin was not affected by the HRGS treatment. The results suggested that free radical oxidation promoted thermal destabilization of myosin in the S-1 portion instead of the rod portion. The altered myosin denaturation pattern due to hydroxyl radical oxidation was likely a cause for functionality changes in oxidatively stressed myofibrillar proteins in meat processing. [Copyright &y& Elsevier]

Abstract: Two P-type Ca transporters, the plasma membrane Ca-ATPase (PMCA) and the sarcoplasmic reticulum (SR) Ca-ATPase (SERCA), play a crucial role in maintaining Ca homeostasis, controlling contractility and contributing to excitably and cell signalling in smooth muscle cells. There is considerable structural homology between the two Ca-ATPases; they both have transmembrane spanning regions, have similar ATP-phosphorylated intermediaries, counter transport protons and are regulated by several second messengers. They both also exist in several isoforms and have many splice variants, which presumably impart some of their tissue specific functions. We describe the relative contribution of PMCA and the Na–Ca exchanger to Ca efflux in relaxation to smooth muscle, including recent data from transgenic mice, which has begun to elucidate the specific contributions of individual isoforms to Ca signalling. We then consider Ca release and uptake into the SR in smooth muscle. Experiments investigating the distribution of SERCA in smooth muscle cells have provided new insights into control of SR luminal Ca, and the effects of SR Ca load on signalling, is discussed. This is followed by a detailed consideration of the interactions between the surface membrane and SR membrane pumps, exchangers and ion channels in smooth muscle, along with their distribution to caveolae and cholesterol-rich membrane domains. Where relevant the importance of these functions to health and disease are noted. We conclude that the dynamic changes in splice variants expressed, constituents of membrane microdomains and environment of the sub-sarcolemmal space, close to the SR, need to be the focus of future research, so that the full importance of Ca transporters to smooth muscle signalling cascades can be better understood. [Copyright &y& Elsevier]

Abstract: Tilapia myosin (2.5mg/ml) was treated by hydrostatic pressure (50–300MPa) for 0–60min to determine the inactivation kinetics of myosin Ca-ATPase. The process of the pressure-induced inactivation of myosin Ca-ATPase included two steps: the first one was an instantaneous pressure-induced inactivation, and the degrees of lost activities, called instantaneous pressure kill (IPK) values, increased with elevated pressure. The second one, the logarithm of residual activity of myosin ATPase, decreased smoothly during each pressure treatment for 10–60min. However, D values (the time needed for 90% loss of the activity during a treatment at the same pressure) of Ca-ATPase decreased about 50% with per 50MPa increase. In this study, 150MPa was the pressure level that caused apparent myosin denaturation and the typical network structure formation with beyond 50% decrease of myosin Ca-ATPase activity. [Copyright &y& Elsevier]

Abstract: Since Ca2+-ATPase is a major determinant of calcium homeostasis in the lens, we examined the expression of Ca2+-ATPase by calcium. An immortalized human lens epithelial cell line, HLE B-3, was treated with thapsigargin to inhibit sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) releasing calcium from intracellular stores. Isoforms of the plasma membrane Ca2+-ATPase (PMCA) and SERCA were quantified by Western blot and quantitative real time reverse transcription polymerase chain reaction. We showed that both PMCA1 and SERCA3 isoform protein and mRNA are upregulated two- to three-fold in thapsigargin-treated HLE B-3 cells in a time and dose-dependent manner. Thapsigargin did not change the protein or mRNA levels of PMCA2, 3, 4 or SERCA2b. Considering the harmful effects of increased intracellular calcium levels, the upregulation of both SERCA and PMCA pumps suggests it is a compensatory mechanism to restore the calcium concentration to the physiological resting level. [Copyright &y& Elsevier]

Abstract: To utilize fishery waste products as functional food material, the shrimp head protein hydrolysate (SHPH) was produced from three species of shrimp wastes, Northern pink shrimp, Endeavour shrimp and black tiger shrimp, by enzymatic hydrolysis. The SHPH was used as a natural food preservative by adding to lizardfish myofibrils at concentrations ranging from 2.5% to 10%. Their effects on the state of water and the denaturation of myofibrils during dehydration were evaluated. The amount of monolayer and multilayer water in myofibrils containing SHPH were higher than those without SHPH (control). DSC analyses revealed that the amount of unfrozen water increased significantly after addition of SHPH. The Ca-ATPase inactivation rate of myofibrils containing SHPH decreased during dehydration while 5–7.5% concentrations of SHPH exhibited optimum effect regardless of the species. The results implicated that SHPH can be used as an alternative food preservative for suppressive the dehydration-induced denaturation of myofibrils. [Copyright &y& Elsevier]

Abstract: The effect of the treatment with magnesium sulfate (MgSO4) on Ca-ATPase activity and level of lipid peroxidation of red blood cells from preeclamptic pregnant women was examined because it is known that these parameters are affected with preeclampsia. Red cell ghosts from 11 normotensive and 11 preeclamptic pregnant women, before and after treatment with MgSO4, were assayed for Ca-ATPase activity and level of lipid peroxidation, determined as TBARS or conjugated dienes. It was found that the Ca-ATPase activity is significantly lower and the level of lipid peroxidation is significantly higher in the preeclamptic women with no treatment, as compared to normotensive pregnant women. Both parameters return to normal values after the MgSO4 therapy. These results can be mimicked by in vitro preincubation with MgSO4 of intact red blood cells from preeclamptic pregnant women, without any treatment. Our data indicate that MgSO4 treatment of preeclamptic pregnant women modifies both the Ca-ATPase activity and the level of lipid peroxidation of their red blood cell membranes, reaching values similar to those of normotensive pregnant women. The diminution of the level of lipid peroxidation by MgSO4, can account for the increase in Ca-ATPase activity. [Copyright &y& Elsevier]

Dipolar waves are distinct hallmarks of both the secondary and tertiary structures of α-helical proteins that are immobilized in membrane bilayers or embedded in anisotropic media. We present a simple, semi-empirical approach that exploits the modulation of the amplitude and average of dipolar waves to determine the topology of α-helical proteins. Moreover, we describe the application of this method for the structural determination of a detergent solubilized membrane protein, phospholamban (PLB) that is involved in calcium regulation of cardiac muscle. When combined with high-resolution solid-state NMR data, this method can serve as a fast route for determining the topology of helical membrane proteins solubilized in detergent micelles. [Copyright &y& Elsevier]

P-type ATPases are a large family of membrane proteins that perform active ion transport across biological membranes. In these proteins, the energy-providing ATP hydrolysis is coupled to ion transport of one or two ion species across the respective membrane. The pump function of the investigated pumps is described by a so-called Post-Albers cycle. Main features of the pumping process are (1) a Ping-Pong mechanism, i.e. both transported ion species are transferred successively and in opposite direction across the membrane, (2) the transport process for each ion species consists of a sequence of reaction steps, which are ion binding, ion occlusion, conformational transition of the protein, successive deocclusion of the ions and release to the other side of the membrane. (3) Recent experimental evidence shows that the ion-binding sites are placed in the transmembrane section of the proteins and that ion movements occur preferentially during the ion binding and release processes. The main features of the mechanism include narrow access channels from both sides, one gate per access channel, and an ion-binding moiety that is adapted specifically to the ions that are transported, and differently in both principal conformations. [Copyright &y& Elsevier]

We investigated the effect of chitin hydrolysate made from crustacean shells and cephalopod cartilage on the denaturation and state of water in lizard fish myofibrillar protein (Mf) during frozen storage at −25 °C for 120 days. The chitin hydrolysate (2.5–12.5 g dry weight) was added to 100 g of the Mf, and the changes in the Mf Ca–ATPase activity and the amount of unfrozen water in the Mf were examined during frozen storage.The addition of chitin hydrolysate markedly decreased the inactivation rate of the Mf Ca–ATPase. The amount of unfrozen water in the Mf increased upon the addition of chitin hydrolysate, and then decreased gradually during frozen storage. On the other hand, the amount of unfrozen water in the control dropped drastically during the initial period of frozen storage. At a concentration of over 5.0%, chitin hydrolysates completely suppressed the inactivation of the Ca–ATPase and maximized unfrozen water in Mf.These results suggest that chitin hydrolysates suppress the denaturation of Mf through enhancement of the interaction between the hydration sphere of the Mf and equatorial OH groups of chitin hydrolysate. [Copyright &y& Elsevier]

Osteoblasts, osteocytes and osteoclasts are specialised cells of bone that play crucial roles in the formation, maintenance and resorption of bone matrix. Bone formation and resorption critically depend on optimal intracellular calcium and phosphate homeostasis and on the expression and activity of plasma membrane transport systems in all three cell types. Osteotropic agents, mechanical stimulation and intracellular pH are important parameters that determine the fate of bone matrix and influence the activity, expression, regulation and cell surface abundance of plasma membrane transport systems. In this paper the role of ATPase pumps is reviewed in the context of their expression in bone cells, their contribution to ion homeostasis and their relation to other transport systems regulating bone turnover. [Copyright &y& Elsevier]

In this study, investigated was the effect of the porphyra yezoensis polysaccharides (PPs) on the denaturation of bighead carp (Aristichthys nobilis) myofibrillar protein (Mf) during frozen storage at −18°C for 90d. The PPs (2.5%, 5%, and 7.5%, respectively) was added to 100g of Mf. The changes in the Ca-adenylpyrophosphatase (ATPase) activity and unfrozen water content in Mf were examined to evaluate he denaturation of Mf during frozen storage. Ca-ATPase activity decreased gradually during frozen storage at −18°C upon addition of PPs. By contrast, Ca-ATPase activity in the control group dropped drastically during the first 45d of storage and then further decreased gradually for up to 90d of storage, indicating a biphasic denaturation pattern. PPs addition significantly increased sulfhydryl contents in the Mf of the treatment groups compared with that of the control group (p <0.05) during frozen storage at −18°C. [ABSTRACT FROM AUTHOR]