Does positive selection in octopus haemocyanin indicate functional links to temperature adaptation?
This study has provided the first insight into molecular and structural mechanisms that have enabled octopods to sustain oxygen supply from polar to tropical conditions. Our findings imply modulation of oxygen binding via charge-charge interaction at the protein surface, which stabilize quaternary interactions among functional units to reduce detrimental effects of high pH on venous oxygen release. Of the observed partial haemocyanin sequence, residue 2545 formed a close link between the FU g surface and the active centre, suggesting a role as allosteric binding site. The prevalence of methionine at this site in polar octopods, implies regulation of oxygen affinity via increased sensitivity to allosteric metal binding. High sequence conservation of sites directly involved in oxygen binding indicates that functional modifications of octopod haemocyanin rather occur via more subtle mechanisms, as observed in this study.
The PedsQL can identify changes post-TBI, but fails to consider whether these changes are relevant to the adolescent. Alternate methods of exploring QoL-which emphasize the interaction of social networks and friendships, should be considered to avoid an oblique view of QoL outcomes after TBI.