Matthias Müller / Hans-Georg Koch

Mechanism of membrane protein integration


In bacteria such as E. coli, the vast majority of secreted preproteins are translocated across the cytoplasmic membrane through the evolutionarily conserved protein-conducting Sec translocon, which is composed of the three core subunits SecY, SecE and SecG. In addition, the Sec translocon serves as an integration site for membrane proteins.


For integration into the lipid bilayer, most bacterial membrane proteins engage the Sec translocon as ribosome-associated nascent chains by the help of signal recognition particle (SRP) and its receptor (FtsY). In contrast, translocation of secreted preproteins through the Sec translocon usually is a posttranslational event that requires ATP hydrolysis by the motor protein SecA. Thus the bacterial Sec translocon is gated by two completely different modes. The topic of this project is to describe the two pathways in molecular details, in order to understand how the Sec translocon changes its structure/composition during both modes of operation.


Composite membrane proteins harbouring extended extramembraneous domains will be the target of investigation, because these proteins subsequently require both gating modes of the Sec translocon for their assembly into the membrane. Such proteins will be synthesized in vitro and their stepwise integration into SecYEG-containing membrane vesicles and proteoliposomes will be followed by site-specific cross-linking, BN-PAGE, and use of defined mutant Sec components.



→to the Müller & Koch groups websites


Selected Publications:

Neumann-Haefelin, C., Schäfer, U., Müller, M., and Koch, H.G. (2000) EMBO J. 19, 6419-6426.

Beck, K., Eisner, G., Trescher, D., Dalbey, R.E., Brunner, J., and Müller, M. (2001). EMBO Rep. 8, 709-714.

Beha, D., Deitermann, S., Müller, M., and Koch, H. G. (2003). J. Biol. Chem. 278, 22161-22167.

Eisner, G., Koch, H. G., Beck, K., Brunner, J., and Müller, M. (2003). J. Cell Biol. 163, 35-44.

Alami, M., Lüke, I., Deitermann, S., Eisner, G., Koch, H. G., Brunner, J., and Müller, M. (2003). Mol. Cell 12, 937-946.

Deitermann, S., Sprie, G.S., and Koch, H.G. (2005). J. Biol. Chem. 280, 39077-39085.

Angelini, S., Deitermann, S., and Koch, H.G. (2005). EMBO Rep. 6, 476-481.

Angelini, S., Boy, D., Schiltz, E., and Koch, H.G. (2006). J. Cell Biol. 174, 715-724.

Nishiyama, K., Ikegami, A., Moser, M., Schiltz, E., Tokuda, H. and Müller, M. (2006). J. Biol. Chem. 281, 35667-35676.

Eisner, G., Moser, M., Schäfer, U., Beck, K., and Müller, M. (2006). J. Biol. Chem. 281, 7172-7179.

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