Gated pores in the ferritin protein nanocage

Properties of ferritin gated pores control rates of FMNH2 reduction of ferric iron in hydrated oxide minerals inside the protein nanocage, and are discussed in terms of: ( 1) the conserved pore gate residues ( ion pairs: arginine 72, aspartate 122, and a hydrophobic pair, leucine 110 - leucine 134), ( 2) pore sensitivity to heat at temperatures 30 degrees C below that of the nanocage itself, and ( 3) pore sensitivity to physiological changes in urea ( 1 - 10 mM). Conditions which alter ferritin pore structure/ function in solution, coupled with the high evolutionary conservation of the pore gates, suggest the presence of molecular regulators in vivo that recognize the pore gates and hold them either closed or open, depending on biological iron need. The apparent homology between ferrous ion transport through gated pores in the ferritin nanocage and ion transport through gated pores in ion channel proteins embedded in cell membranes, make studies of water soluble ferritin and the pore gating folding/unfolding a useful model for other gated pores. (c) 2007 Elsevier B. V. All rights reserved.