The molecular mechanism of redox interaction between neuroglobin and cytochrome c.

Redox interaction between heme proteins - neuroglobin (Ngb) and cytochrome c (Cyt c) is considered to contribute to the Ngb-mediated neuroprotection which mechanism is still unclear. We developed a new methodological approach based on resonance Raman spectroscopy to study redox interaction between Ngb and Cyt c and their mutants with amino acid substitutions in their putative interaction surface or Ω-loop. Spectral features of heme c conformational changes during electron transfer (ET) between wild types (WT) of Ngb and Cyt c were established, such as increase of CS bond vibration mode and altering of C-CH groups' vibrations indicating displacement of Cyt c heme in its crevice. Furthermore, the probability of the planar conformation of Cyt c heme increases under ET between Ngb and Cyt c. ET was disrupted in following redox pairs: Ngb with substitutions E60K/E87K, E60K and WT Cyt c; WT Ngb and Cyt c with substitutions K25E, T78S/K79P and K8E/K27E/K72E/K86E/K87E/E62K/E69K/E90K. Our results suggest that disruption of ET occurs due to both deterioration of proteins' electrostatic interactions and heme conformational changes. We propose the mechanism of Ngb-Cyt c redox interaction: 1) transient complex formation mainly due to electrostatic interactions; 2) heme conformational tuning; 3) electron transfer; 4) complex dissociation.