Neuroglobin dynamics observed with ultrafast 2D-IR vibrational echo spectroscopy

Area of Science:

• Biochemistry
• Structural Biology
• Spectroscopy

Background:

• Neuroglobin (Ngb) is an oxygen-binding protein found in vertebrate brains, belonging to the globin family.
• While Ngb shares the globin fold with myoglobin (Mb), its amino acid sequence shows limited similarity, with conserved key residues around the heme.
• The CO adduct of Ngb exhibits distinct IR absorption bands (N(3) and N(0)) corresponding to different distal histidine positions.

Purpose of the Study:

• To investigate the equilibrium protein dynamics of the CO adduct of Neuroglobin (Ngb).
• To compare the dynamics of Ngb with specific myoglobin (Mb) mutants (L29F and H64V) that mimic Ngb's heme pocket structure.
• To gain insights into the protein's energy landscape near its folded state.

Main Methods:

• Ultrafast 2D-IR vibrational echo spectroscopy was employed to study protein dynamics.
• Spectral diffusion of the CO vibration was observed by monitoring the time dependence of 2D-IR spectra.
• Comparative analysis was performed between Ngb and Mb mutants L29F and H64V.

Main Results:

• The CO adduct of Ngb and the studied Mb mutants displayed similar heme pocket structures and CO FTIR peak positions.
• 2D-IR spectroscopy revealed that the fast structural fluctuations of Ngb are significantly slower compared to the Mb mutants.
• The observed differences in dynamics suggest distinct protein energy landscapes despite structural similarities.

Conclusions:

• Neuroglobin (Ngb) exhibits slower protein dynamics than myoglobin (Mb) mutants with similar heme pocket structures.
• The findings highlight differences in the protein energy landscape and dynamics between Ngb and Mb.
• This study provides valuable insights into the conformational flexibility and dynamics of globins.