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pubmed:abstractText |
The Fe-histidine stretching (nu(Fe-His)) frequency was determined for deoxy subunits of intermediately ligated human hemoglobin A in equilibrium and CO-photodissociated picosecond transient species in the presence and absence of strong allosteric effectors like inositol(hexakis)phosphate, bezafibrate, and 2,3-bisphosphoglycerate. The nu(Fe-His) frequency of deoxyHb A was unaltered by the effectors. The T-to-R transition occurred around m = 2-3 in the absence of effectors but m > 3.5 in their presence, where m is the average number of ligands bound to Hb and was determined from the intensity of the nu(4) band measured in the same experiment. The alpha1-beta2 subunit contacts revealed by ultraviolet resonance Raman spectra, which were distinctly different between the T and R states, remained unchanged by the effectors. This observation would solve the recent discrepancy that the strong effectors remove the cooperativity of oxygen binding in the low-affinity limit, whereas the (1)H NMR spectrum of fully ligated form exhibits the pattern of the R state.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Research Support, Non-U.S. Gov't,
Research Support, N.I.H., Extramural
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