Hemocyanin oxygen-binding properties of a deep-sea hydrothermal vent shrimp: Evidence for a novel cofactor

✍ Scribed by Lallier, F. H.; Truchot, J.-P.

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 104 KB
• Volume: 277
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/(sici)1097-010x(19970401)277:5<357::aid-jez1>3.0.co;2-o

✦ Synopsis

Rimicaris exoculata is a caridean shrimp from the family Alvinocarididae which forms the dominant species around deep-sea hydrothermal vents from the Mid-Atlantic Ridge (MAR). Seeking respiratory adaptations to the hydrothermal environment, we have analysed the oxygen-binding properties of Rimicaris hemocyanin (Hc) in relation with temperature, pH, and lactate variations. Rimicaris native Hc is mostly composed of hexamers. It showed a high oxygen affinity (P 50 approximately 3 Torr at pH 7.5, 15°C), a large Bohr effect (∆logP 50 /∆pH = -1.87 ± 0.25, n = 6), a moderate lactate effect (∆logP 50 /∆log[lac] = -0.12) and almost no temperature effect (∆H = -1.23 kJ.mol -1 15-35°C). Most surprisingly, dialysis of native hemolymph elicited a large increase of Hc-O 2 affinity, an effect opposite to the usual trend observed for crustacean Hcs. Moreover, this increase in affinity could be reversed by adding an ultrafiltrate of native hemolymph to a dialysed sample, thus unveiling the existence of a dialysable yet unknown cofactor which decreases Hcoxygen affinity.