Structure and function of hydrothermal vent crustacean haemocyanin: an update
Lallier, F.; Camus, L.; Chausson, F.; Truchot, J.-P. (1998). Structure and function of hydrothermal vent crustacean haemocyanin: an update. Cah. Biol. Mar. 39(3-4): 313-316. https://dx.doi.org/10.21411/CBM.A.5426C7A7
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723; e-ISSN 2262-3094
Also appears in:
(1998). Proceedings of the First International Symposium on Deep-Sea Hydrothermal Vent Biology: Funchal, Madeira, Portugal 20-24 October 1997. Cahiers de Biologie Marine, 39(3-4). Station Biologique de Roscoff: Roscoff. 219-392 pp., more
The respiratory pigment of decapod crustaceans is haemocyanin that binds reversibly oxygen to a pair of copper atoms. It is a large extracellular protein, with a blue colour, which has a typical hexameric structure (Markl & Decker, 1992) and a large potential for functional plasticity (Truchot & Lallier, 1992). Although in vivo data would be necessary to infer true physiological adaptations to the vent environment, it is tempting to speculate from the in vitro characteristics of haemocyanin presented in this paper. The quaternary structure seems to be essentially correlated with the taxonomy of the studied species: the two shrimps (C. chacei and R. exoculata) exhibit the usual predominance of hexameric haemocyanin, whereas the crabs (B. thermydron and C. praedator) possess a larger proportion of dodecamers. The subunit composition apparently shows a similar pattern to other crustaceans (Markl & Decker, 1992) but it should be more accurately determined using modern techniques such as mass spectrometry. The functional properties of oxygen binding, however, appear to be related to the respective habitat of each species. R. exoculata and C. praedator, which are believed to live in warmer waters, close to the vent chimneys, exhibit some common functional properties like a moderate Hc-O2 affinity due to one or several unknown factors which decrease this affinity. This unique potential to lower affinity could eventually prove beneficial in the large physico-chemical gradient in which they live. Conversely, C. chacei and B. thermydron which live in cooler waters, among Bathymodiolus and Riftia respectively, exhibit an higher Hc-O2 affinity due to a more pronounced lactate effect. This tentative scheme needs to be substantiated with detailed information on the microenvironment of each species, which in turn would allow in vivo experiments to be conducted in appropriate conditions.
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