DIFFERENCES IN INFRARED STRETCHING FREQUENCY OF CARBON MONOXIDE BOUND TO ABNORMAL HEMOGLOBINS

The infrared stretching frequencies for carbon monoxide (vco) bound to various hemoglobins and myoglobins have been determined. The identity of vcowas confirmed by spectra of12C18O and13C16O derivatives. For human hemoglobins A, F, H, and Chesapeake and sheep hemoglobins A, B, C, and lamb, one narrow CO absorption was found near 1951 cm-1. However, two absorptions of similar area were found for hemoglobin MEmory(α2Aβ263 Tyr), at 1970 and 1950 cm-1, and for hemoglobin Zurich (α2Aβ263 Arg), at 1958 and 1951 cm-1. Thus substitution for the amino acid at position 63 of the β chain (the position of the distal histidine in βA) markedly affected the vcofor the CO bound to that chain but no such effect was evident when the amino acid substitution was at a location more remote from the ligand. These data suggest significant participation of the β63residue in CO binding. Myoglobins from horse heart and sperm whale exhibited maximum CO absorptions at about 1944 cm-1, consistent with stronger CO binding than is the case for hemoglobin A. However, these results demonstrate that the vco, a parameter related to the strength of the iron to CO bond, does not necessarily parallel over-all O2or CO affinities. © 1969, American Chemical Society. All rights reserved.