Structure and function of membrane transporters

Plastids are organelles in cells of algae and higher plants but are also found in some groups of non-photosynthetic organisms, for example in parasites of the genus Apicomplexa. These parasites group a class of obligate intracellular, medical and veterinary important pathogens, including the causative agent of malaria Plasmodium ssp, as well as Toxoplasma gondii. We are interested in the identification of homologous transporters found in plants and parasites, their evolutionary development and biochemical characterization.

Plastids play an essential role in the production and distribution of metabolites, for example photosynthetic carbon fixation, amino acid and fatty acid biosynthesis and ammonia assimilation. All types of plastids are surrounded by at least two membranes, the inner and outer envelope membranes. Several of the envelope membrane proteins are responsible for the transport of metabolites, thereby connecting the metabolism of the cytosol and the stroma. Thus, the plastid envelope membranes are important for the integration of plastids into the metabolism of plant cells.

We are interested in the characterization of various transporters of both the outer and inner envelope membranes at the molecular level. For example, several phosphorylated compounds are transported across the inner envelope membrane in exchange with inorganic phosphate. This process is mediated by a family of plastids phosphate translocators.

It is evident that the families of characterized plastid transporters so far represent only a small fraction of envelope proteins involved in the exchange of metabolites between the cytosol and the plastids. The structures and functions of most transporters remain to be elucidated.

We are interested in the characterization of several of these transporters in Arabidopsis thaliana, the model organism for higher plants, and in Toxoplasma gondii which is a model organism for Apicomplexa.

Our projects involve the identification and cloning of genes encoding plastid membrane proteins, the expression of these genes in plants and yeast, the biochemical characterization of the proteins and finally the determination of the protein structure, for example by crystallization of the proteins.