Protein Transport; Molecular Microbiology;
Membrane Proteins; Molecular Machines
Co-workers: Felicity Alcock, Justin Deme, Barbara Mertins, Augustinas Silale, Merel Damen
Our group seeks to understand the molecular machines which transport macromolecules across cell membranes.
Tat transporter Our major focus is on the Tat protein transport system found in the bacteria cell envelope and which is conserved in the thylakoid membrane of plant chloroplasts. The Tat system is involved in a wide range of fundamental cellular processes in bacteria including energy metabolism, nutrient acquisition, resistance to environmental toxins, and formation of the cell envelope. The Tat pathway is required for the virulence of most human bacterial pathogens and is essential for the survival of pathogenic mycobacteria. In plants the Tat system has an obligatory role in forming the photosynthetic apparatus.
The most unusual feature of the Tat system is that it transports proteins in their folded state. As a consequence, it faces the formidable challenge of moving structured macromolecular substrates across a membrane without compromising the permeability barrier of the membrane to small molecules and ions. It is apparent that the mechanism of Tat transport is radically different from that employed by other protein transporters.
Using the bacterium Escherichia coli as our model system we aim to elucidate the structure and mechanism of the Tat transporter. Additional projects target the mechanisms of other membrane-associated molecular machines.
Techniques Our work is grounded in protein biochemistry and bacterial cell biology to which we add a full range of cutting edge molecular techniques, often in collaboration with local colleagues. These techniques include structure determination (X-ray, NMR, cryoEM), molecular genetics, biophysical analysis (spin-labelling, calorimetry, SEC-MAALS), in vivo and in vitro single molecule fluorescence imaging, structural bioinformatics, and molecular dynamics simulations.
- Berks, B.C. (2015) The twin-arginine protein translocation pathway (review). Ann.Rev.Biochem. http://www.annualreviews.org/doi/pdf/10.1146/annurev-biochem-060614-034251
- Grabarczyk, D.B., Chappell, P.E., Johnson, S., Stelzl, L.S., Lea, S.M., and Berks, B.C. (2015) Structural basis for specificity and promiscuity in a carrier protein/enzyme system from the sulfur cycle. Proc.Natl.Acad.Sci.USA 112: E7166-175.
- Yong, S.C., Roversi, P., Lillington, J., Rodriguez, F., Krehenbrink, M., Zeldin, O.B., Garman, E.F., Lea, S.M., and Berks, B.C. (2014) A complex iron-calcium cofactor catalyzing phosphotransfer chemistry. Science 345: 1170-1173 Abstract Full Text
- Alcock, F., Baker, M.A.B., Greene, N.P., Palmer, T., Wallace, M.I., and Berks, B.C. (2013) Live cell imaging shows reversible assembly of the TatA component of the twin-arginine protein transport system. Proc.Natl.Acad.Sci.USA 110: E3650-E3659
- Rollauer, S.E., Tarry, M.J., Graham, J.E., Jääskeläinen, M., Jäger, F., Johnson, S., Krehenbrink, M., Liu, S.-M., Lukey, M.J., Marcoux, J., McDowell, M.A., Roversi, P., Stansfeld, P.J., Robinson, C.V., Sansom, M.S.P., Palmer, T., Högbom, M., Berks, B.C., and Lea, S.M. (2012) Structure of the TatC core of the twin arginine protein transport system. Nature 492: 210-214
Figure 1: Structures of the two types of integral membrane protein which form the Tat translocation apparatus. The structure of TatA was determined by solution NMR (collaboration with Jason Schnell) and the structure of TatC by X-ray crystallography (collaboration with Susan Lea). Figure courtesy of Phillip Stansfeld
Figure 2: The Tat transport site is formed by substrate-induced TatA oligomerization. We have used advanced fluorescence microscopy techniques to visualize fluorescently-labelled TatA in live bacterial cells. When substrate proteins are available for transport TatA undergoes oligomerization (compare left and right panels). The images in the right hand panel resolve individual Tat transport complexes. Images courtesy of Felicity Alcock and Matthew Baker.
Figure 3: Biophysical analysis of Tat components. A TatC preparation is characterized for homogeneity and native mass by SEC-MALLS (left) and for interaction with a Tat targeting peptide by isothermal titration calorimetry (right). Images courtesy of Sarah Rollauer.
Figure 4: Simulation of a NMR-derived TatA complex model in a phospholipid bilayer suggests that Tat transport may involve thinning and disordering the membrane bilayer. Collaboration with Jason Schnell and Mark Sansom. The TatA complex is shown in section. Water molecules are depicted as green spheres. Phospholipids are not shown. Image courtesy of Sarah Rouse.
Graduate Student and Postdoctoral Positions: Enquiries with CV welcome