Protein targeting, transport, and translocation in the cyanobacterium Synechocystis sp. PCC 6803

• Antragsteller: Professor Dr. Dirk Schneider
• Subject Area: Stoffwechselphysiologie, Biochemie und Genetik der Mikroorganismen
• Term: from 2008 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 43311986

Protein transport and targeting are not well understood in cyanobacteria. In contrast to other bacteria, cyanobacteria contain an internal thylakoid membrane system in addition to the typical cytoplasmic membrane, and it is not clear how cyanobacteria manage to sort specific proteins to internal subcompartments. Since DnaK and DnaJ chaperones have been suggested to be involved in protein targeting in cyanobacteria, we have started to analyze a chaperone network in the mesophilic cyanobacterium Synechocystis sp. PCC 6803 in recent years. Here, we suggest experiments to further define the specific functions of cyanobacterial DnaK and DnaJ chaperones. We focus especially on the properties and function of the Synechocystis DnaK3 protein, which is essential and which has been suggested to bind to cyanobacterial thylakoid membranes. We aim to understand the structural basis of DnaK3 binding to membranes Furthermore, we will analyze the DnaJ co-chaperone Sll1933. Interaction of DnaK3 and Sll1933 with each other as well as with membrane lipids will be analyzed in detail. Additionally, our recent observations have indicated that DnaK1 is specifically involved in chaperoning newly synthesized proteins when they emerge from the ribosome, and this is the first case of a prokaryotic Hsp70 chaperone, possibly binding to ribosomes. Thus, interactions between DnaK1 and ribosomes will also be investigated in detail.

• DFG Programme: Forschungsgruppen
• Subproject of: FOR 929: Dynamics of bacterial membrane proteins