Assignment of the ferriheme resonances of the high-spin forms of nitrophorins 1 and 4 by 1H NMR spectroscopy: comparison to structural data obtained from X-ray crystallography.
In this work, we report the assignment of the majority of the ferriheme resonances of high-spin nitrophorins (NPs) 1 and 4 and compare them to those of NP2, published previously. It is found that the structures of the ferriheme complexes of NP1 and NP4, in terms of the orientation of the histidine imidazole ligand, can be described with good accuracy by NMR techniques and that the angle plot proposed previously for the high-spin form of the NPs (Shokhireva, T. Kh.; Shokhirev, N. V.; Walker, F. A. Biochemistry 2003, 42, 679-693) describes the angle of the effective nodal plane of the axial histidine imidazole in solution. There is an equilibrium between the two heme orientations (A and B), which depends on the heme cavity shape, which can be altered by mutation of amino acids with side chains (phenyl vs tyrosyl) near the potential position where a heme vinyl group would be in one of the isomers. The A:B ratio can be much more accurately measured by NMR spectroscopy than by X-ray crystallography.
Shokhireva
Tatiana Kh
TKh
Department of Chemistry, The University of Arizona, Tucson, Arizona 85721-0041, USA.
Smith
Kevin M
KM
Berry
Robert E
RE
Shokhirev
Nikolai V
NV
Balfour
Celia A
CA
Zhang
Hongjun
H
Walker
F Ann
FA
D018360:Crystallography, X-Ray; D006420:Hemeproteins / Q000737:chemistry* / Q000378:metabolism; D006427:Hemin / Q000737:chemistry* / Q000378:metabolism; D046911:Macromolecular Substances / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D012471:Salivary Proteins and Peptides / Q000737:chemistry* / Q000378:metabolism
D006420:Hemeproteins; D046911:Macromolecular Substances; D012471:Salivary Proteins and Peptides; C090560:nitrophorin; D006427:Hemin