Spectroscopic studies of the heme active site of hemoglobin from Chelidonichthys kumu

Hemoglobin (Hb) from Chelidonichthys kumu was studied by resonance Raman and electronic absorption spectroscopy in the iron(III) and iron(II) states and in the presence of O2 and CO at various pH values. All forms showed the appearance of two ν(C=C) stretching modes around 1620 and 1630 cm-1 in contrast to the single band at about 1620 cm-1 observed in human hemoglobin. The two bands are interpreted as the result of a site specific vinyl group–protein interaction which is lower in C. kumu than human hemoglobin; this has been interpreted as being due to the occurrence of the Ile residue instead of Val in position E11 of both chains of C. kumu Hb. In addition, it is proposed that the different amino acid residues present in the proximal and distal cavities of the α- and β-chains with respect to human hemoglobin are responsible for the marked spectroscopic differences as compared with human hemoglobin, observed in the unligated iron(II) and iron(III) forms. © 1998 John Wiley & Sons, Ltd.