Abstract:This review summarizes recent highlights of our joint work on the structure, evolution, and function of a family of highly complex proteins, the hemocyanins. They are blue-pigmented oxygen carriers, occurring freely dissolved in the hemolymph of many arthropods and molluscs. They are copper type-3 proteins and bind one dioxygen molecule between two copper atoms in a side-on coordination. They possess between 6 and 160 oxygen-binding sites, and some of them display the highest molecular cooperativity observed i… Show more
“…In arcid bivalves Scapharca inaequivalvis, blood oxygen transport mediated by hemoglobin-containing erythrocytes is also impaired by Cd exposure, although in this case the mechanism involves a decrease in hematocrit and hemocyte count, and not in oxygen affinity (Weber et al 1990). Given that the oxygen affinity of respiratory pigments, including hemoglobins and hemocyanins, tends to decrease with increasing temperatures (Burnett 1992, Weber & Vinogradov 2001, Decker et al 2007), the combined action of trace metals, high temperature and low oxygen solubility in the water may strongly limit oxygen uptake and delivery in the respiratory organs of aquatic ectotherms.…”
In light of the current rising mean temperatures and fluctuations in temperature extremes involved in global climate change, a cause-and-effect understanding of the temperaturedependent impacts of additional environmental stressors on marine life is crucial for the elaboration of how marine ecosystems will shape in the future. The thermal environment plays a direct role in the distribution and survival of marine ectotherms through the temperature-dependent effects on their physiology, as well as indirectly by affecting the organism's susceptibility to other biotic and abiotic stressors. We review studies that have investigated the effects of temperature and anthropogenic pollution by trace metals, with a focus on metabolic regulation as a major mechanism that underlies the interactive effects of temperature and metals on the physiology and survival of ectotherms. These studies suggest that impairment of energy metabolism plays a key role in the synergistic effects of these stressors, and we elaborate a mechanistic framework for understanding these interactions. Furthermore, the present study seeks to provide an impetus for future investigations in order to define more precisely the physiological mechanisms and functional properties of temperature-pollution interactions.
“…In arcid bivalves Scapharca inaequivalvis, blood oxygen transport mediated by hemoglobin-containing erythrocytes is also impaired by Cd exposure, although in this case the mechanism involves a decrease in hematocrit and hemocyte count, and not in oxygen affinity (Weber et al 1990). Given that the oxygen affinity of respiratory pigments, including hemoglobins and hemocyanins, tends to decrease with increasing temperatures (Burnett 1992, Weber & Vinogradov 2001, Decker et al 2007), the combined action of trace metals, high temperature and low oxygen solubility in the water may strongly limit oxygen uptake and delivery in the respiratory organs of aquatic ectotherms.…”
In light of the current rising mean temperatures and fluctuations in temperature extremes involved in global climate change, a cause-and-effect understanding of the temperaturedependent impacts of additional environmental stressors on marine life is crucial for the elaboration of how marine ecosystems will shape in the future. The thermal environment plays a direct role in the distribution and survival of marine ectotherms through the temperature-dependent effects on their physiology, as well as indirectly by affecting the organism's susceptibility to other biotic and abiotic stressors. We review studies that have investigated the effects of temperature and anthropogenic pollution by trace metals, with a focus on metabolic regulation as a major mechanism that underlies the interactive effects of temperature and metals on the physiology and survival of ectotherms. These studies suggest that impairment of energy metabolism plays a key role in the synergistic effects of these stressors, and we elaborate a mechanistic framework for understanding these interactions. Furthermore, the present study seeks to provide an impetus for future investigations in order to define more precisely the physiological mechanisms and functional properties of temperature-pollution interactions.
“…These prophenoloxidases are copper-containing enzymes that are closely related to the oxygen transporter hemocyanin. Interestingly, it has been demonstrated that the hemocyanins can be readily converted into phenoloxidases by conformational changes induced by limited proteolysis or chemical treatment (45). In vivo activation of both insect and crustacean hemocyanins has also been reported as an antimicrobial defense response (46,47).…”
Section: And Coptotermes Formosanus (Bab40696) Gastropod Sequences Imentioning
The digestion of lignocellulose is attracting attention both in terms of basic research into its metabolism by microorganisms and animals, and also as a means of converting plant biomass into biofuels. Limnoriid wood borers are unusual because, unlike other wood-feeding animals, they do not rely on symbiotic microbes to help digest lignocellulose. The absence of microbes in the digestive tract suggests that limnoriid wood borers produce all the enzymes necessary for lignocellulose digestion themselves. In this study we report that analysis of ESTs from the digestive system of Limnoria quadripunctata reveals a transcriptome dominated by glycosyl hydrolase genes. Indeed, >20% of all ESTs represent genes encoding putative cellulases, including glycosyl hydrolase family 7 (GH7) cellobiohydrolases. These have not previously been reported in animal genomes, but are key digestive enzymes produced by wood-degrading fungi and symbiotic protists in termite guts. We propose that limnoriid GH7 genes are important for the efficient digestion of lignocellulose in the absence of gut microbes. Hemocyanin transcripts were highly abundant in the hepatopancreas transcriptome. Based on recent studies indicating that these proteins may function as phenoloxidases in isopods, we discuss a possible role for hemocyanins in lignin decomposition. biofuels | cellulase | hemocyanin | phenoloxidase | wood degradation
“…Their basic structure is composed of ten subunits that are self-assembled into a hollow cylinder known as a decamer. In gastropods, decamers can self-associate face-to-face to form stable dimers or didecamers [1,2]. Inoculating mammals with hemocyanins induces a strong immune response that is characterized by a Th1 cytokine profile.…”
Hemocyanins, which boost the immune system of mammals, have been used as carrieradjuvants to promote Ab production against haptens and peptides, as immunostimulants during therapy for bladder carcinoma and as a component in therapeutic vaccines for cancer. These biomedical applications have led to growing interest in obtaining hemocyanins with high immunogenicity. Here, we study the immunological properties of a modified oxidized Concholepas concholepas hemocyanin (Ox-CCH) obtained by the oxidation of its carbohydrates using sodium periodate. We assessed the internalization of Ox-CCH into DCs and its immunogenicity and antitumor effects. Transmission electron microscopy showed no changes in Ox-CCH quaternary structure with respect to native CCH, although proteolytic treatment followed by SDS-PAGE analysis demonstrated that Schiff bases were formed. Interestingly, DCs internalized Ox-CCH faster than CCH, mainly through macropinocytosis. During this process, Ox-CCH remained inside endosome-like structures for a longer period. Mouse immunization experiments demonstrated that Ox-CCH is more immunogenic and a better carrier than CCH. Moreover, Ox-CCH showed a significant antitumor effect in the B16F10 melanoma model similar to that produced by CCH, inducing IFN-γ secretion. Together, these data demonstrate that the aldehydes formed by the periodate oxidation of sugar moieties stabilizes the CCH structure, increasing its adjuvant/immunostimulatory carrier effects.
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