Differences in Fe(II)-N epsilon(His-F8) stretching frequencies between deoxyhemoglobins in the two alternative quaternary structures.

AUTOR(ES)

Nagai, K

RESUMO

Resonance Raman spectra have been obtained of the alpha deoxy and beta deoxy subunits within valency hybrid hemoglobins both in the high-affinity (R) and low-affinity (T) structures. Upon conversion from the R to the T structure, the vibrational frequency of the Fe(II)-N epsilon(His-F8) bond changes from 223 to 207 or 203 cm-1 in the alpha deoxy subunit and from 224 to 220 or 217 cm-1 in the beta deoxy subunit. We estimate that the Fe(II)-N epsilon(His-F8) bond is stretched by the R leads to T transition 3 times more in the alpha subunit (0.024 A) than in the beta subunit (0.0085 A) and, accordingly, the strain energy developed in that bond is 8 times larger in the alpha than in the beta subunit. Hence, the oxygen affinity of the alpha and beta subunits may be regulated by different mechanisms.

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