Plastids are plant-specific cell organelles, which perform many specialized and essential functions. Interestingly, plastids called apicoplasts were also found in Apicomplexa, a large group of parasites causing severe diseases like malaria (Plasmodium) or toxoplasmosis (Toxoplasma), providing evidence that Apicomplexa and plants share evolutionary roots. The apicoplast phosphate translocator (APT) belongs to a family of plastid phosphate transporters which connect plastids with the cellular metabolism and thus have important physiological functions. Most importantly, the disruption of the APT gene in Toxoplasma gondii leads to immediate death of the parasite which clearly shows the importance of this transporter for growth of the parasites. Elucidating the structure of APT at atomic resolution would be a major step forward in deciphering the transport mechanism at the molecular level and will also open the way to rational design of drugs against pathogenic organisms such as T. gondii.
The three-dimensional structure of molecules can be determined by X-ray crystallography. In this project, a collaboration with Prof. Pebay-Peyroula in Grenoble (France), we want to elucidate the structure of the APT from T. gondii by crystallizing the isolated and purified protein.
The APT protein had been produced in yeast and a purification protocol have been established. The next steps in the project are:
1. Refining the protein production by using different detergents and buffers.
2. Elucidating the quality of the protein preparation by different techniques like Themal Shift Assays or Dynamic Light Scattering.
3. Large scale purification of the protein.
4. Crystallization of APT by using the Vapor Diffusion Method or Lipidic Cubic Phases.
5. Determining the structure of the protein crystal.