Studies on cobalt myoglobins and hemoglobins. Proton magnetic resonance investigation of the subunit interaction in iron-cobalt hybrid hemoglobins

The paramagnetically shifted proton nuclear magnetic resonance spectra of iron-cobalt hybrid hemoglobins [α(Co)₂β(Fe)₂ and α(F3)₂β(Co)₂], as well as those of deoxy forms of cobalt hemoglobin, iron hemoglobin, and their isolated chains, have been measured at 360 MHz. The proton NMR signals of the deoxy forms of iron and cobalt hemoglobins were individually assigned to each subunit. The NMR spectral charcteristics of the α subunits in deoxycobalt hemoglobin, as well as those in deoxy-α(Co)₂β(Fe)₂, were found to be quite different from those of β(Co)₂ subunits or isolated α(-SH) chain. Upon ligation of carbon monoxide to the β(Fe)₂ subunits in α(Co)₂β(Fe)₂, the spectral properties of deoxy-α(Co)₂ subunits became similar to those of the deoxy-β(Co)₂ subunits. No significant change in the NMR spectrum of the β(Co₂) subunits was observed in α(Fe)₂β(Co)₂ upon ligation of carbon monoxide to the α(Fe)₂ subunits. These observations show the linkage of the electronic structure of the prosthetic groups with the subunits cooperatively in hemoglobin, as well as the inequivalence of the subunits. This is the first report on the paramagnetically shifted proton NMR spectra of the cobalt-substituted hemoproteins.