Functionally distinct haemoglobins of the cryopelagic Antarctic teleost Pagothenia borchgrevinki.

Pagothenia borchgrevinki, has a higher haemoglobin concentration than other Antarctic notothenioids and the high oxygen capacity may correlate with the relatively active mode of life of this fish. The fish has five haemoglobins (Hb C, Hb 0, Hb 1, Hb 2 and Hb 3) with Hb 1 accounting for 70–80% of the total, and Hb C being present in trace amounts. Hb 1 and Hb 2 are functionally similar in terms of Bohr and Root effects. Hb 3 has a weaker Bohr effect than Hb 1 and Hb 2, and the Root effect is similar to that of Hb 1. Hb 0 has a strong Bohr effect and the Root effect is enhanced to a larger extent by the physiological effectors chlorides and phosphates than that of the other components with the exception of Hb C. The heats of oxygenation are lower than those of temperate fish haemoglobins. Temperature variations may have a different effect on the functional properties of each haemoglobin, and chloride and phosphates may play an important role in the conformational change between the oxy and deoxy structures. The complete amino acid sequences of Hb 1 and Hb 0, as well as partial N-terminal or internal sequences of the other haemoglobins, have been established. The high multiplicity of functionally distinct haemoglobins indicates that P. borchgrevinki, has a specialized haemoglobin system.