Quinone mediated Reductive Iron Mobilization from non heme binding bacterial ferritin: Impact of size and substituents

Abstract

About 25% of the total body iron is present inside a hollow nanocage protein called “ferritin”, which is mostly intracellular. Although ferritin releases iron in a controlled fashion for various cellular metabolic activities, the mechanism of its release, in vivo, remains unclear and debatable Physiological reducing agent, NADH, is inefficient in releasing the ferritin iron, when used alone. As reported earlier, the reductive iron mobilization from ferritin nanocage largely depends upon the reduction potential of electron transfer mediators. However, the current work utilizes eight Quinone’s (benzoquinone, anthraquinone and naphthoquinone analogues) which differ in size and substituents attached and reduction potential to mediate electron transfer from NADH to the ferritin mineral core. Among these, naphthoquinone analogous such as plumbagin and juglone released higher amount of iron from ferritin owing to its efficient electron relay abilities. Electron relay abilities of the mediators at neutral pH followed the order. Naphthoquinone analogous > benzoquinone > anthraquinone. In agreement to the Marcus ET theory, our current observations suggest that the mediators with E1/2 values at well separated ranges from that of the reducing agents and ferritin prove to be better electron relay molecules. This ET mechanism of Quinone’s can be exploited for iron removal during biological iron overload conditions but also provide the insight towards microbial iron acquisition processes.