Van Doorslaer Sabine, Trandafir Florin, Harmer Jeffrey R, Moens Luc, Dewilde Sylvia
SIBAC Laboratory, Department of Physics, University of Antwerp, Antwerp, Belgium.
SIBAC Laboratory, Department of Physics, University of Antwerp, Antwerp, Belgium.
Biophys Chem. 2014 Jun;190-191:8-16. doi: 10.1016/j.bpc.2014.03.007. Epub 2014 Apr 8.
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.
电子顺磁共振（EPR）数据显示，野生型人类神经球蛋白（NGB）及其H64Q和F28L点突变体的铁（（13）C -）氰化物配合物与哺乳动物肌红蛋白和血红蛋白的氰化物配合物之间存在很大差异。这些点突变涉及NGB中构成血红素远端口袋的残基，会引起与氰化物配体稳定性变化相关的较小但仍很显著的变化。此外，首次使用戴维斯电子核双共振（ENDOR）测定了氰化物连接的马心肌红蛋白（hhMb）中氰化物碳的完整（13）C超精细张量。这些实验数据与基于（13）C NMR数据和理论模型的早期预测不一致，揭示了模型假设中的重大缺陷。相同的ENDOR程序还允许部分测定氰化物连接的NGB和H64QNGB的相应（13）C超精细张量。这些（13）C参数与氰化物连接的hhMb的参数有显著差异，并对我们目前关于血红素环境如何影响通过EPR和NMR在氰化物连接的血红素蛋白中获得的磁参数的理论理解提出了挑战。
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