2011-07-30 02:00 PM
Protein translocation across the plastid membranes
(Roman Ladig, Uwe Bodensohn, Christian Ehmann, Ken Fischer, Lucia E. Groß, Anna Klinger, Christoph Ruland, Laura Schaupp, Katharina Wiesemann)
The eukaryotic cell is characterized by a high degree of compartimentalisation. In general, almost all proteins residing in the various organelles are synthezied on cytosolic ribosomes and are co- or postranslationally imported (e.g. into the endoplasmic reticulum or the peroxisomes). For this purpose, sophisticated systems for proper recognition, targeting and translocation are required, which can be adapted to cellular or environmental changes. Although the mechanisms are different for the single compartments, general principles of these processes can be derived. The endosymbiontic organelles (mitochondria and chloroplasts) are exceptional since they are bound by two envelope membranes across which they have to import more than 90% of their protein endowment.
Studying plant chloroplasts, we like to understand how the eukaryotic cell organizes such kind of transport processes. Thereby, we try to understand not only the initial processes of protein recognition and targeting to the organellar surface, but investigate also the involved multiproteinaceous membrane-bound translocons (TOC and TIC), which facilitate the passage of plastid proteins across the membranes. To solve the questions of how the import process is regulated and energized, how the involved proteins act together and how the translocon look-like and a molecular level and how they function is the main objective of our studies.