Haemocyanin structure and function of an hydrothermal vent crab, Cyanagraea praedator
Chausson, F.; Lallier, F. (1997). Haemocyanin structure and function of an hydrothermal vent crab, Cyanagraea praedator, in: Biologie des sources hydrothermales profondes = Biology of deep-sea hydrothermal vents: Journées d'échanges du Programme DORSALES = DORSALES Workshop Roscoff 6-8 octobre 1997. Cahiers de Biologie Marine, 38(2): pp. 117-118
In: (1997). Biologie des sources hydrothermales profondes = Biology of deep-sea hydrothermal vents: Journées d'échanges du Programme DORSALES = DORSALES Workshop Roscoff 6-8 octobre 1997. Cahiers de Biologie Marine, 38(2)[s.n.][s.l.]. 111-149 pp., meer
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723; e-ISSN 2262-3094, meer
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| Abstract |
The hydrothermal vent crab, Cyanagraea praedato, which is found close to the chimney, is exposed to low level of oxygen and high temperatures for fairly long periods. C. praedator is subject to extremely variable environmental conditions, so it had to develop adaptation mecanisms, in particular respiratory adaptations, to survive. We have studied the structure and functions of Cyanagraea haemocyanin, and compared our results with those obtained on Bythograea thermydron. The quaternary structure of Cyanagraea haemocyanin is a typical crustacean haemocyanin structure (Mark & Deeker, 1992). Dodecamers and hexamers, visible under transmission electronic microscopy, can be separated by gel chromatography along with some monomers. When dodecamers and hexamers were subjected to native polyacrylamide gel electrophoresis, hexamers appeared to be composed of four monomeric subunits whereas dodecamers comprised an additional subunit. Estimations of the molecular weight of the monomeric subunits by SDS-polyacrylamide gel clectrophoresis ranged between 85 kDa and 66 kDa. Functional properties of haemocyanin oxygen-binding were investigated with a diffusion chamber using the step by step procedure. Oxygen affinity was moderately high, with P50 = 5.2 Torr at 15 degree C and pH 7.6, slightly above values obtained with B. thermydron Hc (Sanders et al, 1988). However the Bohr effect was surprisingly intense (deltalog P50/deltapH < -2) especially for a brachyuran species (Truchot, 1992). Conversely, oxygenation was apparently endothermic with deltaH= 15.5 kJ.mo super(1-1) between 4 and 35 degree C at pH 7.6. Considering that, as a crab gets closer to a vent, the increase in temperature is probably accompanied by a decrease in pH, the affinity for oxygen by Cyanagraea Hc would actually decrease, but in a limited extent due to a compensation of this high Bohr effect by a positive intrinsic heat of oxygenation. |
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