The influence of the Cys46/Cys55 disulfide bond on the redox and spectroscopic properties of human neuroglobin.

The influence of the Cys46/Cys55 disulfide bond on the redox and spectroscopic properties of human neuroglobin. J Inorg Biochem. 2017 Oct 16;178:70-86 Authors: Bellei M, Bortolotti CA, Di Rocco G, Borsari M, Lancellotti L, Ranieri A, Sola M, Battistuzzi G Abstract Neuroglobin is a monomeric globin containing a six-coordinate heme b, expressed in the nervous system, which exerts an important neuroprotective role. In the human protein (hNgb), Cys46 and Cys55 form an intramolecular disulfide bond under oxidizing conditions, whose cleavage induces a helix-to-strand rearrangement of the CD loop that strengthens the bond between the heme iron and the distal histidine. Hence, it is conceivable that the intramolecular disulfide bridge modulates the functionality of human neuroglobin by controlling exogenous ligand binding. In this work, we investigated the influence of the Cys46/Cys55 disulfide bond on the redox properties and on the pH-dependent conformational equilibria of hNgb, using UV-vis spectroelectrochemistry, cyclic voltammetry, electronic absorption spectroscopy and magnetic circular dichroism (MCD). We found that the SS bridge significantly affects the heme Fe(III) to Fe(II) reduction enthalpy (ΔH°'rc) and entropy (ΔS°'rc), mostly as a consequence of changes in the reduction-induced solvent reorganization effects, without affecting the axial ligand-binding interactions and the polarity and electrostatics of the heme environmen...
Source: Journal of Inorganic Biochemistry - Category: Biochemistry Authors: Tags: J Inorg Biochem Source Type: research