Functional characterisation of the haemoglobins of the migratory notothenioid fish Dissostichus eleginoides

This study addresses the primary structure, the oxygen-binding properties and the CO-rebinding kinetics of the haemoglobins of the Patagonian toothfish Dissostichus eleginoides. D. eleginoides belongs to the family Nototheniidae, the most diversified of the suborder Notothenioidei, mostly exhibiting an Antarctic distribution. Some of its features are typical of Antarctic species, some are not. For instance, D. eleginoides appears not to have functional antifreeze glycoproteins (consistent with its non-Antarctic distribution). In contrast, it has a major and a minor haemoglobin (similar to many Antarctic notothenioids), and their very low oxygen affinity does not follow the trend of other non-Antarctic notothenioids and appears typical of cold-adapted species. Moreover, the amino-acid sequence reveals high identity with the globins of Antarctic notothenioids, arguing in favour of a common origin within notothenioids, and indicates that the primary structure of the major and minor haemoglobins has undergone modifications only to a limited extent. The ligand-rebinding kinetics of the major haemoglobin of D. eleginoides indicate a strong stabilisation of the quaternary T state at lower pH values.