NMR titration curves of histidine ring protons. 11. Near-heme histidine residues of deoxy- and oxymyoglobins

Abstract

Proton NMR titration curves of the histidine C.epsilon.-H resonances of the deoxy and oxy forms of human, horse and sperm whale myoglobins (Mb) were determined and compared with the results for the met and azide forms. One extra titrating resonance (H-8) was observed for each deoxy-Mb compared with the corresponding met-Mb, and an extra resonance (H-9) was observed for the oxy-Mb form. These resonances correspond to the 2 additional resonances previously described for azide-Mb. These resonances should be assigned to the near-heme histidine residues.