A Possible Mechanism for Redox Control of Human Neuroglobin Activity

Neuroglobin (Ngb) promotes neuron survival under hypoxic/ischemic conditions. In vivo and in vitro assays provide evidence for redox-regulated functioning of Ngb. On the basis of X-ray crystal structures and our MD simulations, a mechanism for redox control of human Ngb (hNgb) activity via the influence of the CD loop on the active site is proposed. We provide evidence that the CD loop undergoes a strand-to-helix transition when the external environment becomes sufficiently oxidizing, and that this CD loop conformational transition causes critical restructuring of the active site. We postulate that the strand-to-helix mechanics of the CD loop allows hNgb to utilize the lability of Cys46/Cys55 disulfide bonding and of the Tyr44/His64/heme propionate interaction network for redox-controlled functioning of hNgb.