The Calgary 2013 iGEM team used the human ferritin wild type as reporter protein on a test strip. They expressed the human ferritin heavy and light chain E. coli. In the cells, the ferritin produced its characteristic iron core. With the help of fenton chemistry they were able to cause a coloring of the iron core and produced the prussian blue iron complex. Beside the function as reporter, the team mentioned the capability of ferritin to produce nanoparticles with other metal ions.
This capability of human ferritin to bind different metal ions makes it suitable for the recycling of different valuable metal ions. When nanoparticles are formed inside the ferritin, they have the advantage that they are easily soluble in water due to the protein shell. Furthermore, the maximal inner diameter of 8nm causes a size restriction of the nanoparticles inside the human ferritin (Butts et al., 2008). This restriction is desirable for industrial applications Quelle!!!. The wild type ferritin has reactive amino acids on the outside and inside of the protein shell, causing nanoparticle synthesis at both surfaces. An optimization of the wild type human ferritin can therefore favor a unified production of different nanoparticles.
To improve the ferritins capability to direct metal ions to its inside and to increase its ability to form gold and silver nanoparticles, we used a mutated version of the human ferritin heavy chain (HUHF). Following Christopher A. Butts et al. (2008) we removed reactive cysteine and histidine residues from exterior of the HUHF and added additional cysteine residues at the interior. This way the production of nanoparticles at the exterior surface is prevented or at least decreased.
In Figure X the amino acid sequence alignment of the wild type human ferritin and the mutated human ferritin is shown. The exterior residues C91R, C103A, C131S, H14D and H106Q, and in the interior the residues E65C, E141C, E148C, K87Q and K144C were mutated. All changed site are also marked in Figure X. The mutation have no influence on the structure of the ferritin as shown in Figure X.
Butts, C.A., Swift, J., Kang, S., Di Costanzo, L., Christianson, D.W., Saven, J.G., and Dmochowski, I.J. (2008).. Directing Noble Metal Ion Chemistry within a Designed Ferritin Protein † , ‡. Biochemistry 47: 12729–12739.
