title: Structural and functional characterization of haemocyanin from the anemone hermit crab Dardanus calidus.
abstract: 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).
authors.affiliation: Dipartimento di Scienze Applicate ai Biosistemi, Università di Cagliari, Cittadella Universitaria, I-09042 Monserrato, Cagliari, Italy.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Podda
authors.forename: Barbara
authors.initials: B
authors.lastname: Manconi
authors.forename: Alessandra
authors.initials: A
authors.lastname: Olianas
authors.forename: Mariagiuseppina
authors.initials: M
authors.lastname: Pellegrini
authors.forename: Irene
authors.initials: I
authors.lastname: Messana
authors.forename: Marco
authors.initials: M
authors.lastname: Mura
authors.forename: Massimo
authors.initials: M
authors.lastname: Castagnola
authors.forename: Bruno
authors.initials: B
authors.lastname: Giardina
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Sanna
mesh_terms: D000818:Animals; D002850:Chromatography, Gel; D003445:Crustacea; D004591:Electrophoresis, Polyacrylamide Gel; D006433:Hemocyanins / Q000737:chemistry* / Q000502:physiology*; D011487:Protein Conformation
chemical_list: D006433:Hemocyanins