Influence of globin structures on the state of the heme. IV. Ferrous low spin derivatives

摘要: Studies of high spin ferrous and ferric derivatives led us to conclude that in the quaternary R structure state hemes is similar free alpha beta subunits, but T a tension acts on which tries pull iron proximal histidine further from plane porphyrin. We have now studied effect inositol hexaphosphate (IHP) three low compounds hemoglobin with O2, CO, NO. IHP failed switch carbonmonoxy- oxyhemoglobin A state, merely caused transition an as yet undefined modification structure. known cause Kansas. found this induces red shifts visible absorption bands appearance shoulder side band; these changes are very weak slightly stronger As already noted by previous authors, addition nitrosylhemoglobin all uv CD spectra, sulfhydryl reactivities, exchangeable proton resonances normally associated leads transition, accompanied large Soret bands. Experiments nitrosyl hybrids show predominantly subunits. In accompanying paper Maxwell Caughey (J. C. W. S. (1976), Biochemistry, following issue) report NO without gives single ir stretching frequency characteristic for six-coordinated hemes; causes second band, intensity equal first, five-coordinated hemes. Taken together, results either rupture or at least dramatic bond heme-linked histidine, such equilibrium set up between five- hemes, biased toward ones The reason why can nitrosyl-, not A, be weakening iron-histidine unpaired electron short Fe-NO length.