EPR analysis of cyanide complexes of wild-type human neuroglobin and mutants in comparison to horse heart myoglobin.
Electron paramagnetic resonance (EPR) data reveal large differences between the ferric ((13)C-)cyanide complexes of wild-type human neuroglobin (NGB) and its H64Q and F28L point mutants and the cyanide complexes of mammalian myo- and haemoglobin. The point mutations, which involve residues comprising the distal haem pocket in NGB, induce smaller, but still significant changes, related to changes in the stabilization of the cyanide ligand. Furthermore, for the first time, the full (13)C hyperfine tensor of the cyanide carbon of cyanide-ligated horse heart myoglobin (hhMb) was determined using Davies ENDOR (electron nuclear double resonance). Disagreement of these experimental data with earlier predictions based on (13)C NMR data and a theoretical model reveal significant flaws in the model assumptions. The same ENDOR procedure allowed also partial determination of the corresponding (13)C hyperfine tensor of cyanide-ligated NGB and H64QNGB. These (13)C parameters differ significantly from those of cyanide-ligated hhMb and challenge our current theoretical understanding of how the haem environment influences the magnetic parameters obtained by EPR and NMR in cyanide-ligated haem proteins.
SIBAC Laboratory, Department of Physics, University of Antwerp, Antwerp, Belgium. Electronic address: sabine.vandoorslaer@uantwerpen.be.
Sabine
S
Van Doorslaer
SIBAC Laboratory, Department of Physics, University of Antwerp, Antwerp, Belgium.
Florin
F
Trandafir
Centre for Advanced Imaging, University of Queensland, St Lucia, QLD, 4072, Australia.
Jeffrey R
JR
Harmer
PPES Laboratory, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium.
Luc
L
Moens
PPES Laboratory, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium.
Sylvia
S
Dewilde
D000818:Animals; D003486:Cyanides / Q000032:analysis / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005914:Globins / Q000737:chemistry* / Q000235:genetics*; D006321:Heart; D006736:Horses; D006801:Humans; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry*; D009211:Myoglobin / Q000737:chemistry*; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics*; D000078787:Neuroglobin; D017354:Point Mutation
D003486:Cyanides; D050505:Mutant Proteins; D009211:Myoglobin; D009419:Nerve Tissue Proteins; D000078787:Neuroglobin; D005914:Globins
Cyanide binding; Electron paramagnetic resonance; Neuroglobin