Structure of carboxymyoglobin in crystals and in solution.
The configuration of the heme-carbonyl group upon binding of carbon monoxide to sperm whale myoglobin (Mb) in crystals is evaluated on the basis of infrared spectroscopic methods. Multiplets of the totally symmetric C-O stretching mode are observed for the heme-bound ligand near 1933, 1944, and 1967 cm-1, corresponding to three different heme-carbonyl conformers. Variations in the relative proportions of these conformers can be induced by incorporation of small fractions of metMb or deoxyMb into MbCO crystals. The configuration of the iron-carbonyl with respect to the immediate coordination environment of the heme iron is assigned for each v(CO) stretching frequency on the basis of a detailed comparison of the three-dimensional structures of the heme environments of MbCO, metMb, and deoxyMb defined by crystallographic methods. The structures of the three heme-carbonyl conformers account for the v(CO) infrared absorption bands that can be observed for MbCO in solution.
D000818:Animals; D002248:Carbon Monoxide; D003461:Crystallography; D006418:Heme; D007501:Iron; D008024:Ligands; D009211:Myoglobin; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D014907:Whales
D008024:Ligands; D009211:Myoglobin; D006418:Heme; D002248:Carbon Monoxide; D007501:Iron