SPECTROSCOPIC STUDIES OF THE HEME ACTIVE-SITE OF HEMOGLOBIN FROM CHELIDONICHTHYS KUMU

Hemoglobin (Hb) from Chelidonichthys kumu was studied by resonance Ram an and electronic absorption spectroscopy in the iron(III) and iron(II ) states and in the presence of O-2 and CO at various pH values. All f orms showed the appearance of two v(C=C) stretching modes around 1620 and 1630 cm(-1) in contrast to the single band at about 1620 cm(-1) ob served in human hemoglobin. The two bands are interpreted as the resul t 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 o f both chains of C. kumu Hb. In addition, it is proposed that the diff erent amino acid residues present in the proximal and distal cavities of the alpha- and beta-chains with respect to human hemoglobin are res ponsible for the marked spectroscopic differences as compared with hum an hemoglobin, observed in the unligated iron(II) and iron(III) forms. (C) 1998 John Wiley & Sons, Ltd.