INTERACTION BETWEEN PHOSPHATE AND PROTEIN, AND RESPIRATION OF LLAMA, HUMAN FETUS AND HORSE

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  • 1 January 1978
    • journal article
    • research article
    • Vol. 359  (5) , 547-558
Abstract
The sequence analysis of llama (Lama glama) Hb is described. The chains were separated, cleaved by trypsin, quantitatively characterized and sequenced in 9 sequenator. Llama Hb differs from human Hb in that it was 25 different amino acids in the .alpha. chain and 24 different amino acids in the .beta. chain. The interaction between protein and phosphate is discussed. The earlier finding that the O2 affinity of the llama Hb is dependent on its content of 2,3-bisphosphoglycerate is interpreted here as a mutation of the 2,3-bisphosphoglycerate contact position .beta.2 His in human Hb to .beta.2 Asn in llama Hb, whereby one of the four 2,3-biphosphoglycerate contact points is interrupted. This interruption gives rise to a diminished reduction of intrinsic oxygen affinity in the Hb molecule and explains, on a molecular basis, the increased oxygen affinity of the llama Hb and the high-altitude respiration of the llama. The increased O2 affinity of human fetal Hb is explained (according to previous physiological investigations on blood and fetal Hb) by the inactivation of the phosphoglycerate contact point .beta.143 His in the adult Hb by mutation to .gamma.143 Ser in the fetal Hb. With respect to respiration in horses (2,3-bisphosphoglycerate contact .beta.2 Gln), measurement of atomic parameters show that the amide group of the glutamine is situated close enough to the 2,3-bisphosphoglycerate oxygen to from a hydrogen bond with the phosphate. The explanation of the low-altitude respiration of the horse lies in the fact that glutamine and histidine fulfill stereochemically an identical function.