CIRCULAR-DICHROISM SPECTROSCOPY OF LUCINA-I HEMOGLOBIN

The monomeric hemoglobin from the mollusc Lucina pectinata (HbI) repre sents an interesting model system for the study of heme-related circul ar dichroic (CD) bands in view of the highly asymmetric distribution o f aromatic residues around the heme pocket revealed by the X-ray cryst al structure, The CD spectra of both ferrous and ferric HbI derivative s exhibit negative CD bands in the Soret and ultraviolet region with a n enhanced ellipticity of the heme N and L bands in the near-UV region , In contrast, the magnitude of the Cotton effect in the visible and S oret regions is comparable to that observed in other hemoproteins, The spectrum of the carbon monoxide derivative shows a surprising similar ity with that observed for the soybean leghemoglobin carbon monoxide a dduct, A common structural feature in the two proteins is the presence in the distal pocket of two Phe residues (B9 and B10) the aromatic ri ngs of which are perpendicular to the heme plane. (C) 1997 Federation of European Biochemical Societies.