Glutathionylation induced structural changes in oxy human hemoglobin analyzed by backbone amide hydrogen/deuterium exchange and MALDI-mass spectrometry

Authors : Mitra G, Muralidharan M, Narayanan S, Pinto J, Srinivasan K, Mandal AK

Publication Year : 2012

Abstract :

Glutathionyl hemoglobin, a posttranslationally modified form of hemoglobin, has been reported to serve as a marker of oxidative stress in several clinical conditions. This modification causes perturbations in the hemoglobin function by increasing oxygen affinity and reducing cooperativity. Moreover glutathionylation of sickle hemoglobin was reported to lead to a significant reduction in the propensity of sickling of erythrocytes. The root cause of the above functional abnormality is not known in detail as the crystal structure of the molecule is yet to be discovered. In this study, we investigated the effects of glutathionylation on quaternary structure of hemoglobin using hydrogen/deuterium exchange (H/DX) based mass spectrometry. H/DX kinetics of nine peptides from α and β globin chains of hemoglobin were analyzed to understand the conformational change in deoxy to oxy transition of normal hemoglobin and structural perturbations associated with glutathionylation of oxy hemoglobin. Significant structural changes brought about by the glutathionylation of oxy hemoglobin were observed in the following regions of globin chains: β86-102, β1-14, α34-46, β32-41, β130-146, β115-129, β73-81. Isotope exchange kinetics monitored through mass spectrometry is a useful technique to understand structural perturbation on posttranslational modification of proteins in solution phase.