Conformational Dynamics in Neuroglobin

Neuroglobin (Ngb) is a heme protein that belongs to the family of hexacoordinated hemoglobins. The physiological role of this protein is not well understood, but several plausible functions have been proposed such as oxygen carrier, oxygen sensor, NO scavenger and protectant against oxidative damage. To understand the mechanism of Ngb interactions with diatomic ligands we have determined kinetics and thermodynamics of conformational changes associated with CO dissociation and rebinding to human neuroglobin (hNgb) and rat neuroglobin (rNgb) using photoacoustic calorimetry, photothermal beam deflection, and transient absorption spectroscopy. The impact of the internal disulfide bond found in hNgb on the ligand migration was investigated by characterizing the time profile of structural changes associated with CO photo-dissociation from the following mutants: rNgbGly46Cys, hNgbCys46Gly, hNgbCys55Ser, hNgbCys120Ser, hNgbCys55SerCys120Ser and hNgb reduced with DTT. Moreover, to determine the role of amino acid residues located in the heme binding pocket on the ligand - protein interactions in Ngb, the kinetics and energetics of the ligand dissociation from His64Gln, His64GlnVal68Phe, Val68Phe, Phe49Ala, Phe49Leu and Phe49Asp mutants were determined.View Large Image | View Hi-Res Image | Download PowerPoint Slide