How is leghemoglobin involved in peribacteroid membrane degradation during nodule senescence?

Abstract

An increase in the rate of succinate and glutamate uptake by isolated symbiosomes from French bean nodules was observed in the presence of iron plus H 2O 2. The lipid bilayer, and not proteins involved in transport, seems to be the major target of radical attack. Leghemoglobin in the presence of a 6-fold excess of H 2O 2 (where heme breakdown and iron release occurred) provoked also an increase in peribacteroid membrane permeability. In contrast, this hemoprotein in the presence of a 2-fold excess of H 2O 2 (where a protein radical was generated) was without effect. We suggest that in vivo the release of heme iron may constitute the major process concerning the involvement of leghemoglobin in the degradation of the peribacteroid membrane during nodule senescence.