Nuclear magnetic resonance of high-spin ferric hemoproteins. Assignment of proton resonances in met-aquo myoglobins using deuterium-labeled hemes

Abstract

The high-field 1H NMR spectra of sperm whale high-spin (S = 5/2) met-aquo myoglobin reconstituted with various specifically deuterated protohemins and deuterohemins are shown to lead to the resolution of 17, and the unambiguous assignment of 12, of the 22 possible heme resonances in the native protein. Two nonheme paramagnetically shifted methyl peaks are assigned to the distal valine E11. The heme methyl shift pattern is the same as in models, but reflects a much greater rhombic or in-plane asymmetry. The resonance positions of the meso and pyrrole protons confirm the presence of coordinated water and suggest that these peaks may be useful in probing the occupation of the sixth site in high-spin hemoproteins. The deviations from Curie law of vinyl and probable propionate group resonances are interpreted in terms of temperature-dependent orientations of these conformationally flexible side chains. © 1980, American Chemical Society. All rights reserved.