Identification Of Residues Crucial For The Interaction Between Human Neuroglobin And The Alpha-Subunit Of Heterotrimeric G(I) Protein

Mammalian neuroglobin (Ngb) protects neuronal cells under conditions of oxidative stress. We previously showed that human Ngb acts as a guanine nucleotide dissociation inhibitor (GDI) for the alpha-subunits of heterotrimeric G(i/o) proteins and inhibits the decrease in cAMP concentration, leading to protection against cell death. In the present study, we used an eukaryotic expression vector driving high-level expression of human wild-type Ngb or Ngb mutants that either exhibit or lack G(alpha i1) activities in human cells. We demonstrate that the GDI activity of human Ngb is tightly correlated with its neuroprotective activity. We further demonstrate that Glu53, Glu60, and Glu118 of human Ngb are crucial for both the neuroprotective activity and interaction with G(alpha i1). Moreover, we show that Lys46, Lys70, Arg208, Lys209, and Lys210 residues of G(alpha i1) are important for binding to human Ngb. We propose a molecular docking model of the complex between human Ngb and G(alpha i1).