FUNCTIONAL, SPECTROSCOPIC AND STRUCTURAL-PROPERTIES OF HEMOGLOBIN FROM CHAMOIS (RUPICAPRA-RUPICAPRA) AND STEINBOCK (CAPRA-HIRCUS-IBEX)

The functional and spectroscopic properties of chamois (Rupicapra rupi capra) and steinbock (Capra hircus ibex) haemoglobin (Hb) have been st udied with special reference to the action of allosteric effectors and temperature. Moreover, the amino acid sequences of the N-terminal seg ments of the alpha- and beta-chains have been determined. The present results indicate that chamois and steinbock Hbs display a low affinity for O2, which appears to be modulated in vivo by Cl- ions rather than 2,3-bisphosphoglycerate. The Bohr effect for O2 binding to chamois an d steinbock Hb is higher than for reindeer and bovine Hbs, being simil ar to that of human Hb. Moreover, the temperature-dependence of oxygen ation appears intermediate between that of human and reindeer Hbs. E.p .r. and absorption spectroscopic properties of the ferrous nitrosylate d derivative of chamois and steinbock Hbs suggest that both haemoprote ins are in a low-affinity conformation even in the absence of InsP6. T he reduced effect of polyphosphates on the functional and spectroscopi c properties of chamois and steinbock Hb agree with amino acid differe nces in the N-terminal segment of the beta-chains (i.e. the deletion o f Val(NA1) and the replacement of His(NA2), present in human Hb, and G ln(NA2), present in horse Hb, by Met). The molecular mechanism modulat ing the basic reaction of O2 with chamois and steinbock Hb may be link ed to specific physiological needs related to the high-altitude habita ts of these two animals.