The oxygen-binding modulation of hemocyanin from the Southern spiny lobster <Emphasis Type="Italic">Palinurus gilchristi</Emphasis> |
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Authors: | Alessandra Olianas Barbara Manconi Daniela Masia Maria T Sanna Massimo Castagnola Susanna Salvadori Irene Messana Bruno Giardina Mariagiuseppina Pellegrini |
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Institution: | (1) Department of Sciences Applied to Biosystems, University of Cagliari, Cittadella Universitaria, 09042 Monserrato (CA), Italy;(2) Institute of Biochemistry and Clinical Biochemistry, Faculty of Medicine, Catholic University “Sacro Cuore”, Largo F. Vito 1, 00168 Rome, Italy;(3) Department of Animal Biology and Ecology, University of Cagliari, Viale Poetto 1, 09126 Cagliari, Italy |
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Abstract: | Arthropod hemocyanins transport and store oxygen and are composed of six subunits, or multiples thereof depending on the species.
Palinurus gilchristi hemocyanin is found only as 1 × 6-mers, as normally occurs in spiny lobsters. An alkaline pH and removal of calcium ions
induce a wholly reversible dissociation into monomers. The oxygen-binding properties of 1 × 6-meric hemocyanin from P. gilchristi were investigated with respect to pH and modulating effect exerted by calcium, lactate and urate. The oxygen affinity was
highly affected by pH in the presence of calcium ions, while in its absence the Bohr coefficient became 60% lower. The protein
is insensitive to lactate, but affected by urate which markedly increased hemocyanin–oxygen affinity, acting as the physiological
major positive effector. Calcium ions decrease oxygen affinity at low concentration range (0–1 mM), while as concentration
becomes higher than 100 mM, the oxygen affinity increases, indicating the presence of two independent types of calcium-binding
sites with high and low affinity, respectively. The previous hypothesis, that the presence of high-affinity binding sites
in addition to low affinity ones could be a characteristic feature of Palinuran hemocyanins, has been tested by analyzing,
with respect to calcium–hemocyanin interaction, three other species belonging to Palinura. |
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Keywords: | Hemocyanin Oxygen affinity Calcium effect Urate effect Palinurus gilchristi |
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