Structural and functional characterization of haemocyanin from the anemone hermit crab Dardanus calidus.
Oxygen-binding to haemocyanin (Hc) is generally an exothermic process, with overall enthalphy of oxygenation varying from species to species. A number of crustacean Hcs showed a null or reduced enthalphy of oxygenation, among others, the anomuran Pagurus bernhardus and Paralithodes camtscaticae possess a completely temperature-independent oxygen-binding in a wide range of temperature and pH. Functional analysis performed on purified native, hexameric and dodecameric Hc forms of the anemone hermit crab Dardanus calidus allowed to calculate the enthalphy of oxygenation values that resulted equal to -36.2, -33.8 and -26.8 kJ/mol, respectively. Thus, the temperature sensitivity of oxygen binding of D. calidus Hc is in contrast with the temperature independence reported for P. bernhardus and P. camtscaticae, suggesting a high Hc functional heterogeneity within Anomura. Functional characterization also evidenced a strong oxygen affinity modulation by protons (DeltalogP(50)/DeltapH = -0.97) and lactate [DeltalogP(50)/Deltalog(lactate) = -0.38], and a significant decrease in cooperativity by physiological concentration of lactate (n(50) from 2.8 to 1.7 at pH 7.5).
Podda
Gabriella
G
Dipartimento di Scienze Applicate ai Biosistemi, Università di Cagliari, Cittadella Universitaria, I-09042 Monserrato, Cagliari, Italy.
Manconi
Barbara
B
Olianas
Alessandra
A
Pellegrini
Mariagiuseppina
M
Messana
Irene
I
Mura
Marco
M
Castagnola
Massimo
M
Giardina
Bruno
B
Sanna
Maria Teresa
MT
D000818:Animals; D002850:Chromatography, Gel; D003445:Crustacea; D004591:Electrophoresis, Polyacrylamide Gel; D006433:Hemocyanins / Q000737:chemistry* / Q000502:physiology*; D011487:Protein Conformation
D006433:Hemocyanins