Haemoglobin Polymorphisms in the Echidna, Tachyglossus Aculeatus

The echidna, Tachyglossus aculeatus, has two haemoglobins and polymorphic variants of both have been described. Haemoglobins Hb-IA, Hb-IB and Hb-IIA have been separated and their oxygen binding parameters studied. Hb-IIA has a markedly higher oxygen affinity and lower cooperativity than the polymorphs ofhaemoglbin I. In phosphate buffer, pH 7·1 and 25°C, Hb-IIA has an oxygen half-saturation pressure (Pso) of 1·3 kPa and a Hill coefficient of 2·4, whereas the polymorphic forms of Hb-I have P so values of about 1·6 kPa and Hill coefficients of about 2·9. Differences in diphosphoglyceric acid interactions account for some of these differences. When the polymorphic forms of haemoglobin I were compared at pH 7 ·1, Hb-IA had a AHo value of -27·9 kJjmol and a Hill coefficient of 2·9, whereas Hb-IB had a AHo value of -31·7 kJjmol and a Hill coefficient of 3·0.These results are discussed in terms of selection value to the animal and in relation to the molecular structure of haemoglobins.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Oxygen Binding of Monotrene Haemoglobins II. Fixation of Functionally Non-equivalent Haemoglobins in the Echidna Population

Hosken¹,

Boettcher²

1978

“…The discontinuous buffer system of Poulik (1957) at pH 8·6 was used. The echidna haemoglobin used was a mixture of Hb-IB and Hb-IIA (Cooper et al 1973).…”

Section: Electrophoresismentioning

confidence: 99%

Oxygen Binding of Monotreme Haemoglobins I. Oxygen Binding Parameters of the Haemoglobins of Platypus, Ornithorhynchus anatinus, and Echidna, Tachyglossus aculeatus

Hosken¹

1978

Oxygen binding parameters have been determined for echidna and platypus haemolysates. At pH 7· 1 and 25°C platypus haemoglobin with an oxygen half-saturation pressure (Pso) of 2·4 kPa has a lower oxygen affinity than echidna haemoglobin with a Pso of 1·6 kPa. The AH o of oxygenation of platypus haemoglobin is -38·9kJ/mol which is more exothermic than the -29·7kJ/mol of echidna haemoglobin. Platypus haemoglobin has a steeper alkaline Bohr curve than echidna haemoglobin, while both haemoglobins show high levels of cooperativity at various temperatures and pH values. It appears that diphosphoglyceric acid modulates the affinity of echidna and platypus haemoglobins to different extents. This information is interpreted in terms of the steric effects of ligand binding originating in the amino acid sequence differences of these two species.

“…In Parts I and II of this series (Whittaker et al 1972(Whittaker et al , 1973) the fractionation of the haemoglobins and of the globin chains from the south-eastern Australian echidna Tachyglossus aculeatus aculeatus (Cooper et al 1973) was reported, together with the amino acid sequences of the a-and f3-g1obin chains of the major haemoglobin component, Hb-IB.…”

Section: Introductionmentioning

confidence: 99%

Studies on Monotreme Proteins. III. Amino Acid Sequence of the a- and ß-Globin Chains of the Minor Haemoglobin from the Echidna, Tachyglossus Aculeatus Aculeatus

Eo¹,

Wk²,

Whittaker³

1973

Echidnas exhibit polymorphism in their haemoglobins. The minor component in animals from the mainland of Australia is Hb-IIA, which can be identified by electrophoretic migration rate and separated by chromatography on DEAE-Sephadex. This minor component has IX-and fi-globin chains which were only partially separated by chromatography on carboxymethylcellulose columns. By tryptic digestion of the partially purified chains, followed by fractionation by paper ionophoresis and chromatography, the component pep tides from the IX-and fi-chains were isolated and their amino acid sequences determined.The fi-chain was identical in amino acid sequence with the fi-chain from the major haemoglobin component, and the IX-chain varied in only nine positions from the IX-chain of the major haemoglobin component, Hb-IB, whose amino acid sequences were previously reported. From the number of changes in sequence, its presence in all echidnas, and the proportion of the minor component, it must be the product of non-allelic IX-chain genes.There were no changes in "contact site" residues in the IX-chain of the minor haemoglobin compared with those present in the major haemoglobin.