MOLECULAR CHARACTERIZATION OF THE FUNCTIONALLY DISTINCT HEMOGLOBINS OF THE ANTARCTIC FISH TREMATOMUS-NEWNESI

Antarctic fish of the family Nototheniidae usually have a single major hemoglobin (Hb 1), often a second, minor component (Hb 2, about 5% of the total), and traces of another component (Hb C, less than 1%). The se are functionally similar Bohr and Root effect hemoglobins. All spec ies of other highly endemic fish families so far investigated also hav e one single major hemoglobin. The hematological features of the notot heniid Trematomus newnesi are remarkably different. It is the only Ant arctic species in which Hb 1 and Hb 2 display only a very weak Bohr ef fect and no Root effect. Perhaps consequentially, Hb C (the only compo nent showing regulation of oxygen binding by protons and other effecto rs) is not present in traces but accounts for 20-25% of the total. The primary structure of the three hemoglobins of T. newnesi and of Root effect HbC present in trace amounts in another nototheniid (Pagothenia bernacchii) is discussed in relationship with oxygen binding and in t erms of molecular and stereochemical models. The hemoglobin multiplici ty, the oxygen binding features of Hb 1 and Hb 2, and the presence of functionally distinct components, thus reveal that the oxygen transpor t of T. newnesi has unique characteristics.