Functional, spectroscopic and structural properties of haemoglobin from chamois (Rupicapra rupicapra) and steinbock (Capra hircus ibex)

Abstract

The functional and spectroscopic properties of chamois (Rupicapra rupicapra) and steinbock (Capra hircus ibex) haemoglobin (Hb) have been studied with special reference to the action of allosteric effectors and temperature. Moreover, the amino acid sequences of the N-terminal segments 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 and steinbock Hb is higher than for reindeer and bovine Hbs, being similar to that of human Hb. Moreover, the temperature-dependence of oxygenation appears intermediate between that of human and reindeer Hbs. E.p.r. and absorption spectroscopic properties of the ferrous nitrosylated derivative of chamois and steinbock Hbs suggest that both haemoproteins are in a low-affinity conformation even in the absence of InsP6. The reduced effect of polyphosphates on the functional and spectroscopic properties of chamois and steinbock Hb agree with amino acid differences in the N-terminal segment of the beta-chains (i.e. the deletion of Val(NA1) and the replacement of His(NA2), present in human Hb, and Gln(NA2), present in horse Hb, by Met). The molecular mechanism modulating the basic reaction of O2 with chamois and steinbock Hb may be linked to specific physiological needs related to the high-altitude habitats of these two animals.

Low‐temperature sensitivity and enhanced Bohr effect in red deer (Cervus elaphus) haemoglobin: a molecular adaptive strategy to life at high altitude and low temperature

“…The amplitude of the Bohr effect (Δ log p 50 /ΔpH, where ΔpH = 6.5–8.0) for O 2 binding to red deer Hb is –0.47 under stripped conditions, and –0.51 and –0.57 in the presence of Cl − and/or of both Cl − and GriP 2 , respectively. These values are similar to those reported for chamois and steinbock Hb [11], but higher than those observed for other ruminant Hbs such as reindeer [19], sheep ( Ovis aries ), mouflon ( Ovis gmelini musimon ) [20] and ox ( Bos tauros ) [2].…”

“…Two Hb phenotypes (lane 2 and 3) differing in the α‐chain are compared with the heterozygote (lane 1) containing both of them. Separation was by PAGE in the presence of acetic acid, 8 m urea and Triton X‐100 [10–12]. The gel was stained with 0.5% Coomassie blue.…”

“…A specific case is represented by Hbs from chamois ( Rupicapra rupicapra ) and steinbock ( Capra hircus ibex ), whose habitats are characterized by both high altitudes and low temperatures. These two Hb systems have been shown to display an enhanced pH‐dependence of O 2 affinity that has been considered a peculiar molecular strategy that may characterize those ruminants that are specialized for living at high altitude [11].…”

The Bohr effect of haemoglobin in vertebrates: an example of molecular adaptation to different physiological requirements

“…The Bohr coefficient for oxygen binding (Δlog P 50 /ΔpH at the midpoint of the transition) to red deer Hb is −0.51 in the presence of physiological concentration of chloride. These values are similar to those reported for chamois and steinbock (Ascenzi et al. 1993), but higher than those observed for other ruminant Hbs such as reindeer (Giardina et al.…”

“…The Bohr coefficient for oxygen binding (Dlog P 50 /DpH at the midpoint of the transition) to red deer Hb is )0.51 in the presence of physiological concentration of chloride. These values are similar to those reported for chamois and steinbock (Ascenzi et al 1993), but higher than those observed for other ruminant Hbs such as reindeer ), sheep (Corda et al 1997), mouflon (Coletta et al 1992), and ox (Giardina et al 1990a). The increased Bohr effect for red deer Hb oxygenation compared with other ruminant Hbs may be of importance for living at high altitude.…”