Distal mutation modulates the heme sliding in mouse neuroglobin investigated by molecular dynamics simulation

Neuroglobin (Ngb), a hexa-coordinated hemoprotein primarily expressed in the brain and retina, is thought to be involved in neuroprotection and signal transduction. Ngb can reversibly bind small ligands such as O₂ and CO to the heme iron by replacing the distal histidine which is bound to the iron as the endogenous ligand. In this work, molecular dynamics (MD) simulations were performed to investigate the functionally related structural properties and dynamical characteristics in carboxy mouse neuroglobin and three distal mutants including single mutants H64V, K67T and double mutant H64V/K67T. MD simulations suggest that the heme sliding motion induced by the binding of exogenous ligand is affected by the distal mutation obviously. Accompanying changes in loop flexibility and internal cavities imply the structural rearrangement of Ngb. Moreover, the solvent accessibility of heme and some crucial residues are influenced revealing an interactive network on the distal side. The work elucidates that the key residues K67 at E10 and H64 at E7 are significant in modulating the heme sliding and hence the structural and physiological function of Ngb.