Relationship of function and higher order structure of abnormal hemoglobin.

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In order to address the relationship between oxygen binding function (allostery) and quaternary structure changes of hemoglobin A (Hb A), we have studied on structure and function of abnormal hemoglobin by ultraviolet (UV) circular dichroism (CD) and UV resonance Raman (UVRR) spectroscopy. The results were summarized as follows :(1) A study of quaternary structure change of Hb by UVCD : We examined UVCD spectra of abnormal hemoglobin with amino acid substitution at α1-β2 subunit interface (References, 1, 2).(1) Heme and protein structure of Hb M Iwate and Hb M Boston characterized by UV and visible resonance Raman study (References, 3, 4).(2) Structural and functional relationship of hemoglobin by UVRR : Tyr and Trp RR bands excited with 235nm changed upon deoxy->oxy(or CO) structure transition. We clarified which Tyr or Trp residue contributed to these changes using abnormal hemoglobin, NO and metal-hybrid Hb (References, 5-7).From these results, we have elucidated that Tyr and/or Trp residues at α1-β2 subunit interface are critically important for hemoglobin allostery. These aromatic residues contribute not independently but cooperatively to higher order protein structure transition of hemoglobin.