SPECTRAL CHANGES AND ALLOSTERIC TRANSITION IN TROUT HEMOGLOBIN

PREVIOUS results have shown that two of the haemoglobin components from trout blood, Hb trout I and Hb trout IV, have different functional properties, which may be correlated directly with their physiological role (see ref. 1 for review). Thus, Hb trout I, which displays cooperative ligand binding at all pH values, completely lacks heterotropic interactions; on the other hand, these interactions are clearly evident in Hb trout IV, for which lowering of pH, or addition of organic phosphates, produces a large decrease in oxygen affinity and in cooperativity (n drops from 2.3 at pH 8 to ~1 at pH 6)