The reaction of neuroglobin with potential redox protein partners cytochrome b 5 and cytochrome c

Previously identified, potentially neuroprotective reactions of neuroglobin require the existence of yet unknown redox partners. We show here that the reduction of ferric neuroglobin by cytochrome b 5 is relatively slow ( k = 6 × 10 2 M −1 s −1 at pH 7.0) and thus is unlikely to be of physiological significance. In contrast, the reaction between ferrous neuroglobin and ferric cytochrome c is very rapid ( k = 2 × 10 7 M −1 s −1 ) with an apparent overall equilibrium constant of 1 μM. Based on this data we propose that ferrous neuroglobin may well play a role in preventing apoptosis.