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BMC Evolutionary Biology

, 10:214

First Online: 16 July 2010Received: 04 April 2010Accepted: 16 July 2010

Abstract

BackgroundElevated blood O2 affinity enhances survival at low O2 pressures, and is perhaps the best known and most broadly accepted evolutionary adjustment of terrestrial vertebrates to environmental hypoxia. This phenotype arises by increasing the intrinsic O2 affinity of the hemoglobin Hb molecule, by decreasing the intracellular concentration of allosteric effectors e.g., 2,3-diphosphoglycerate; DPG, or by suppressing the sensitivity of Hb to these physiological cofactors.

ResultsHere we report that strictly fossorial eastern moles Scalopus aquaticus have evolved a low O2 affinity, DPG-insensitive Hb - contrary to expectations for a mammalian species that is adapted to the chronic hypoxia and hypercapnia of subterranean burrow systems. Molecular modelling indicates that this functional shift is principally attributable to a single charge altering amino acid substitution in the β-type δ-globin chain δ136Gly→Glu of this species that perturbs electrostatic interactions between the dimer subunits via formation of an intra-chain salt-bridge with δ82Lys. However, this replacement also abolishes key binding sites for the red blood cell effectors Cl, lactate and DPG the latter of which is virtually absent from the red cells of this species at δ82Lys, thereby markedly reducing competition for carbamate formation CO2 binding at the δ-chain N-termini.

ConclusionsWe propose this Hb phenotype illustrates a novel mechanism for adaptively elevating the CO2 carrying capacity of eastern mole blood during burst tunnelling activities associated with subterranean habitation.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2148-10-214 contains supplementary material, which is available to authorized users.

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Autor: Kevin L Campbell - Jay F Storz - Anthony V Signore - Hideaki Moriyama - Kenneth C Catania - Alexander P Payson - Joseph

Fuente: https://link.springer.com/article/10.1186/1471-2148-10-214







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