Hb natal or α2(minus Tyr-Arg)β2: a high oxygen affinity α chain variant with a deleted carboxy-terminus resulting from a TAC → TAA (Tyr→ terminating codon) mutation in codon α140

Abstract The discovery is reported of a fast-moving α chain variant (Hb Natal) which is characterized by a shortened α 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 α 2 globin gene, which causes a change in the codon for tyrosine to a terminating codon. Hb Natal or α 2 (minus Tyr-Arg) β 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 α140 in the oxygenation-deoxygenation process.