Molecular adaptation to hibernation: the hemoglobin of Dryomys nitedula

Abstract

The oxygen binding properties of Dryomys nitedula hemoglobin (Hb) were investigated as a function of pH both in the absence and in the presence of its physiological cofactors (i.e. chloride ions and 2,3-biphosphoglyceric acid) and at different temperatures. Moreover, the alpha- and beta-chains of the Dryomys Hb were partially sequenced. The results obtained show that the effects of Bohr protons, chloride ions, organic phosphates and temperature are significantly lower for Dryomys Hb than for human Hb. Thus, the increase in Hb oxygen affinity, resulting from the reduction of red cell organic phosphates and body temperature that occurs during hibernation, is advantageous for loading oxygen at the lung level without compromising oxygen release at the tissues, as could occur if Dryomys Hb had similar functional properties to those of other non-hibernating mammals. Furthermore, it is possible that the reduced Bohr effect may moderate the potential effects of increased CO(2) associated with prolonged apnea on the loading and unloading of oxygen. Moreover, the overall heat of oxygenation (Delta H) for Dryomys Hb is much less exothermic than that of the human Hb and it is completely independent of the 2,3-biphosphoglyceric acid concentration.

Hemoglobin function and allosteric regulation in semi-fossorial rodents (family Sciuridae) with different altitudinal ranges

“…of the stripped Hb). In conjunction with results from other recent studies (Clementi et al, 2003;Natarajan et al, 2013;Storz et al, 2009;Storz et al, 2010a;Storz et al, 2012;Weber, 1992), the data summarized in Table1 indicate that rodent Hbs are generally far less responsive to DPG than the Hbs of humans and many other mammals.…”

Deer mouse hemoglobin exhibits a lowered oxygen affinity owing to mobility of the E helix

“…The P 50 values of human and lowland deer mouse hemolysates were 1216 and 1929 Pa, respectively (Clementi et al, 2003;Storz et al, 2010) in 100 mM HEPES buffer pH 7.4 with 100 mM Cl À at 310 K. Under these conditions, lowland deer mouse hemoglobin has the higher P 50 value. At the oxygen-binding site, the distal histidine residues His58 and His63 are located in the E helix and the proximal histidine residues His87 and His92 are located in the F helix.…”

Molecular Cloning and Evolutionary Analysis of Hemoglobin α-Chain Genes in Bats

“…Because Hb in plants and other nonanimal organisms does not function in oxygen transport, this attribute probably accompanied the emergence of multicellular animals (Vinogradov et al 2006). Different species live in different ecological conditions, and their Hb has evolved differing functional features (Clementi et al 2003;Giardina et al 2004). Hb discharges its function by changing its structure.…”