The oxygen-binding modulation of hemocyanin from the Southern spiny lobster Palinurus gilchristi.
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 x 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 x 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.
Olianas
Alessandra
A
Department of Sciences Applied to Biosystems, University of Cagliari, Cittadella Universitaria, 09042 Monserrato (CA), Italy.
Manconi
Barbara
B
Masia
Daniela
D
Sanna
Maria T
MT
Castagnola
Massimo
M
Salvadori
Susanna
S
Messana
Irene
I
Giardina
Bruno
B
Pellegrini
Mariagiuseppina
M
D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006433:Hemocyanins / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D033521:Palinuridae / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D013053:Spectrophotometry; D014527:Uric Acid / Q000378:metabolism
D021122:Protein Subunits; D014527:Uric Acid; D019344:Lactic Acid; D006433:Hemocyanins; D010100:Oxygen; D002118:Calcium