Calculated electrostatic gradients in recombinant human H‐chain ferritin

Calculations to determine the electrostatic potential of the iron storage protein ferritin, using the human H‐chain homopolymer (HuHF), reveal novel aspects of the protein. Some of the charge density correlates well with regions previously identified as active sites in the protein. The three‐fold channels, the putative ferroxidase sites, and the nucleation sites all show expectedly negative values of the electrostatic potential. However, the outer entrance to the three‐fold channels are surrounded by regions of positive potential, creating an electrostatic field directed toward the interior cavity. This electrostatic gradient provides a guidance mechanism for cations entering the protein cavity, indicating the three‐fold channel as the major entrance to the protein.