Nuclear magnetic resonance studies on myoglobin.
2015-11-19T08:48:27Z (GMT) by
Nuclear magnetic resonance spectroscopy (NMR) studies of the paramagnetic haemoprotein equine cyanometmyoglobin are presented. Many significant NMR assignments in both the proton and carbon-13 spectra of equine cyanometmyoglobin have been obtained. Notably the full proton and carbon-13 assignments for all four haem methyl groups have been obtained, resolving some previous ambiguity surrounding the assignment of the haem 3-methyl group, and full proton assignments for the haem 4-vinyl group, which is unresolved from the diamagnetic envelope in the one dimensional proton spectrum, have been obtained by use of two dimensional proton-proton shift correlation spectroscopy (COSY). Assignments are also presented for the ubiquitous proximal histidine residue, which plays a role in modulating the activity of the iron centre, as well as for certain other physiologically relevant haem pocket nuclei, providing a valuable basis for future studies of the strueture-function relationships not only of equine cyanometmyoglobin, but also of those other related haemoproteins for which it can be used as a model. It has been demonstrated that the COSY technique, which prior to the commencement of this work was believed to be inapplicable to paramagnetic species, since the line broadening and rapid loss of coherence caused by paramagnetic induced relaxation was thought to interfere with COSY peak detection, may indeed be profitably applied to the study of paramagnetic haemoproteins. The usefulness of other spectroscopic techniques, previously rarely used in the study of biological macromolecules, such as two dimensional heteronuclear shift correlation spectroscopy, and both one and two dimensional techniques involving the editing of the natural abundance carbon-13 spectrum according to the number of attached protons, to the study of paramagnetic haemoproteins has also been demonstrated.