The blood proteins of the Antarctic icefish Channichthys rhinoceratus: biological significance and purification of the two main components

The lack of hemoglobin and of carbonic anhydrase in the blood of icefish suggest that substantial adaptations of the acid-base balance should occur in order to ensure blood pH homeostasis. The level of peptidic histidyl and of reactive -SH groups per unit of body mass in icefish plasma are 12-13 times higher than those of Notothenia rossii, a common red-blooded Antarctic species. It is proposed that the high level of imidazole ring in icefish plasma improves the non-bicarbonate buffering capacity and that the reactive sulfhydryls are involved in a redox buffer as in some other hypoxia tolerant species. After plasma fractionation on Ultrogel AcA 34, the two main icefish serum proteins have been purified by DEAE cellulose chromatography (IFI) and by HPLC on anion exchange column (IF2). IFI has been identified as a cysteine-rich para-albumin and IF2 as an histidine-rich immunoglobulin-like protein.