[Hemoglobin M Saskatoon alpha 2 beta 2 63 (E7) His--Tyr. Structural identification, hemichrome formation and proteolytic degradation].

During examination of the patient with methemoglobinemia of unclear ethiology abnormal Hb was found in the blood hemolysate. The primary structure determination allowed to identify the variant as Hb M Saskatoon with alpha 2 beta 2 63 (E7) His leads to Tyr substitution, that is the first known case of Hb M Saskatoon bearing in the Soviet Union. From the investigation of some physico-chemical properties it was concluded that not only the distal histidine can play the role of the sixth endogenous ligand at the hemichrome formation. The proteolytic degradation of met Hb M Saskatoon showed, that a shift of the distal residue (E7) to the heme ligand position does not itself lead to a considerable increase of the conformational lability of the protein as in the case of a few hemichrome forms.