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Hb natal or alpha 2(minus Tyr-Arg) beta 2: a high oxygen affinity alpha chain variant with a deleted carboxy-terminus
V B Jogessar1, K Westermeyer, B B Webber
1Department of Haematology, University of Natal, Durban, South Africa.
Abstract:
The discovery is reported of a fast-moving alpha chain variant (Hb Natal) which is characterized by a shortened alpha polypeptide chain because of the deletion of the Tyr-Arg carboxy-terminal residues. Through amplification of appropriate segments of DNA and hybridization with synthetic oligonucleotide probes, it was possible to detect a C----A mutation in codon 140 of the alpha 2 globin gene, which causes a change in the codon for tyrosine to a terminating codon. Hb Natal or alpha 2 (minus Tyr-Arg) beta 2 has a high affinity for oxygen without a Bohr effect and heme-heme interaction. These results provide direct evidence for the importance of the tyrosine residue at alpha 140 in the oxygenation-deoxygenation process.