The Calgary 2013 iGEM team used the human ferritin wild type (BBa_K1189019) as reporter protein on a test strip. They expressed the human ferritin heavy and light chain heterologous using Escherichis coli. In the cells, the ferritin produced its characteristic iron core. With the help of fenton chemistry they were able to dye the iron core by producing the prussian blue iron complex. Beside the function as reporter, the team mentioned the capability of ferritin to produce nanoparticles with other metal ions.
Figure 1: Ferritin is suitable for metal recycling, since it can form e.g. iron, silver and gold nanoparticles in its cavity.
This capability of human ferritin to bind different metal ions makes it suitable for the recycling of different valuable metal ions (Figure 1) (Ensign et al., 2004; Domínguez-Vera et al., 2007). 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 various applications (Castro et al., 2014). 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 (Butts et al., 2008).
Improved Human Ferritin: BBa_K2638999
To improve the ferritins capability to direct metal ions to its inside and to increase its ability to form gold and silver nanoparticles, we constructed a mutated version of the human ferritin heavy chain (HUHF) (BBa_K2638999). 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.
Figure 2: Alignment of the protein sequences of the wild-type and the mutated human ferritin heavy chain. The Alignment was produced with Clustal Omega (Goujon et al., 2010, Sievers et al., 2011).
In Figure 2 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 the interior residues E65C, E141C, E148C, K87Q and K144C were mutated. The mutations have no influence on the structure of the ferritin as shown in Figure 3.
Figure 3: Protein structures of the wild-type human ferritin (A, RCSB ID 4oYN) and the mutated human ferritin (B, RCSB ID 3ES3). Despite the mutations of ten amino acids the ferritin retains its shape. The protein structeres were generated with Chimera (Pettersen et al., 2004).
Outlook
Figure 4: Possible applications of nanoparticles produced with ferritin.
Molecular graphics and analyses performed with UCSF Chimera, developed by the Resource for Biocomputing, Visualization, and Informatics at the University of California, San Francisco, with support from NIH P41-GM103311. 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.
Castro, L., Blázquez, M.L., Muñoz, J., González, F., and Ballester, A. (2014).. Mechanism and Applications of Metal Nanoparticles Prepared by Bio-Mediated Process. Rev. Adv. Sci. Eng. 3.
Ensign, D., Young, M., and Douglas, T. (2004).. Photocatalytic synthesis of copper colloids from CuII by the ferrihydrite core of ferritin. Inorg. Chem. 43: 3441–3446.
Goujon, M., McWilliam, H., Li, W., Valentin, F., Squizzato, S., Paern, J., and Lopez, R. (2010).. A new bioinformatics analysis tools framework at EMBL-EBI. Nucleic Acids Res. 38: W695-699.
Pettersen, E.F., Goddard, T.D., Huang, C.C., Couch, G.S., Greenblatt, D.M., Meng, E.C., and Ferrin, T.E. (2004).UCSF Chimera--a visualization system for exploratory research and analysis. J Comput Chem 25: 1605–1612.
Sievers, F., Wilm, A., Dineen, D., Gibson, T.J., Karplus, K., Li, W., Lopez, R., McWilliam, H., Remmert, M., Söding, J., Thompson, J.D., and Higgins, D.G. (2011). Fast, scalable generation of high-quality protein multiple sequence alignments using Clustal Omega. Mol. Syst. Biol. 7: 539.
Ummartyotin, S., Bunnak, N., Juntaro, J., Sain, M., and Manuspiya, H. (2012). . DSynthesis of colloidal silver nanoparticles for printed electronics. /data/revues/16310748/v15i6/S1631074812000549/.
Wang, L., Hu, C., and Shao, L. (2017a).. The antimicrobial activity of nanoparticles: present situation and prospects for the future. Int. J. Nanomedicine 12: 1227–1249.
Wang, Z., Gao, H., Zhang, Y., Liu, G., Niu, G., and Chen, X. (2017b).. Functional ferritin nanoparticles for biomedical applications. Front. Chem. Sci. Eng. 11: 633–646.
