Molecular adaptation to hibernation: the hemoglobin of Dryomys nitedula.
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.
Clementi
M E
ME
Institute of Biochemistry, Faculty of Medicine, and CNR Institute Chimica del Riconoscimento Molecolare, Catholic University, Largo F. Vito 1, 00168 Rome, Italy. e.clementi@uniserv.ccr.rm.cnr.it
Petruzzelli
R
R
Filippucci
M G
MG
Capo
C
C
Misiti
F
F
Giardina
B
B
D019794:2,3-Diphosphoglycerate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001831:Body Temperature / Q000502:physiology; D002851:Chromatography, High Pressure Liquid; D004588:Electrophoresis, Cellulose Acetate; D006454:Hemoglobins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D006605:Hibernation / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010100:Oxygen / Q000097:blood; D010108:Oxyhemoglobins / Q000378:metabolism*; D011485:Protein Binding; D012377:Rodentia / Q000097:blood / Q000235:genetics / Q000502:physiology*; D013816:Thermodynamics
D006454:Hemoglobins; D010108:Oxyhemoglobins; D019794:2,3-Diphosphoglycerate; D010100:Oxygen