Primary structure and oxygen-binding properties of the hemoglobin from the lesser hedgehog tenrec (Echinops telfairi, Zalambdodonta). Evidence for phylogenetic isolation.

The primary structures of the alpha- and beta-hemoglobin chains of the lesser hedgehog tenrec (Echinops telfairi, Zalambdodonta) are presented. Chain separation was performed by carboxymethyl-cellulose chromatography. The peptides, obtained by tryptic digestion of the oxidized chains, were prefractionated by gel chromatography and isolated by reversed-phase HPLC. For sequence analysis gas and liquid phase sequencers were employed. The tenrec hemoglobin consists of one alpha- and two beta-chains the latter occurring in a 1:1 ratio and differing in beta 16 Gly/Cys and beta 118 Phe/Leu. Two external cysteine residues at beta 16 and beta 52 cause reversible polymerization to octamers and most likely irreversible formation of higher polymers. A comparison of the whole chains and certain positions of tenrec hemoglobin with those of Insectivora sensu strictu, Scandentia and Proto- and Metatheria corroborates a long and independent evolution of tenrec and its phylogenetic isolation from the Insectivora s.str. (hedgehog, musk shrew and mole). Replacements at positions involved in heme and subunit interface contacts are discussed. Compared to human hemoglobin the tenrec pigment shows a low intrinsic oxygen affinity as well as lower chloride and temperature sensitivities, a reduced Bohr effect and a strong response to 2,3-DPG. The possible adaptive significance of these properties is discussed in relation to the large diurnal body temperature variations seen in tenrecs.