University of Dundee

Professor Tracy Palmer FRSE FSB FAAM MEAM

Protein transport across bacterial membranes
Professor of Molecular Microbiology and Head of the Division of Molecular Microbiology
School of Life Sciences, University of Dundee, Dundee
Full Telephone: 
+44 (0) 1382 386464, int ext 86464


Protein Transport in Bacteria

Figure 1. Transmission electron micrograph images of (left panel) E. coli K12 pa

The major research focus of my group is the transport of proteins by the twin arginine protein transport pathway. This pathway, which is found in the cytoplasmic membranes of most bacteria, and the thylakoid membranes of plant chloroplasts, is highly unusual because it transports pre-folded proteins. Protein substrates are targeted to the Tat machinery by N-terminal signal peptides that contain an S/T- R-R-x-F-L-K ‘twin arginine’motif. Our aims are to study the function and mechanism of the Tat protein transporter, and the contribution that it makes to the physiology of bacteria.

Functional studies on the bacterial Tat pathway are carried out in collaboration with Dr Ben Berks, University of Oxford. Using the model organism Escherichia coli, we have identified the tatA, tatB, tatC and tatE genes that encode components of the Tat system. Focusing on the major components, TatA, B and C we are studying their roles in protein transport by a combination of genetics, molecular biology and biochemical techniques.

Our physiological studies on the Tat pathway currently encompass two groups of bacteria. Escherichia coli K12 has some 27 or so Tat substrate proteins. About two thirds of these contain non-covalently bound redox cofactors that are bound prior to export by the Tat pathway. We collaborate with Professor Frank Sargent to genetically define the components required for the assembly of these complex Tat substrates before their interaction with the Tat system. Other substrates of the E. coli Tat system include two amidase enzymes involved in cell wall remodelling and that are critical for cell envelope integrity. In collaboration with the Drug Discovery Unit in the College of Life Sciences we are interested in identifying small molecules that interfere with the activity of the Tat machinery that might be useful precursors to novel antimicrobial drugs

We have recently started collaborating with Prof Bill Hunter (Division of Biological Chemistry and Drug Discovery) to investigate the structure and function of Type VII protein secretion systems from Gram positive bacteria.



BI40051 - 4A05 Bacterial Membrane Biology

BI32052 Molecular Microbiology & Immunology


Alcock, F., Stansfeld, P. J., Basit, H., Habersetzer, J., Baker, M. A., Palmer, T., Wallace, M. I. and Berks, B. C. (2016) Assembling the Tat protein translocase. eLife. 5
Cao, Z., Casabona, M. G., Kneuper, H., Chalmers, J. D. and Palmer, T. (2016) The type VII secretion system of Staphylococcus aureus secretes a nuclease toxin that targets competitor bacteria. Nature microbiology. 2, 16183
Jager, F., Zoltner, M., Kneuper, H., Hunter, W. N. and Palmer, T. (2016) Membrane interactions and self-association of components of the Ess/Type VII secretion system of Staphylococcus aureus. FEBS letters. 590, 349-357
Munnoch, J. T., Widdick, D. A., Chandra, G., Sutcliffe, I. C., Palmer, T. and Hutchings, M. I. (2016) Cosmid based mutagenesis causes genetic instability in Streptomyces coelicolor, as shown by targeting of the lipoprotein signal peptidase gene. Scientific reports. 6, 29495
Parthasarathy, S., Parapatla, H., Nandavaram, A., Palmer, T. and Siddavattam, D. (2016) Organophosphate Hydrolase Is a Lipoprotein and Interacts with Pi-specific Transport System to Facilitate Growth of Brevundimonas diminuta Using OP Insecticide as Source of Phosphate. The Journal of biological chemistry. 291, 7774-7785
Warne, B., Harkins, C. P., Harris, S. R., Vatsiou, A., Stanley-Wall, N., Parkhill, J., Peacock, S. J., Palmer, T. and Holden, M. T. (2016) The Ess/Type VII secretion system of Staphylococcus aureus shows unexpected genetic diversity. BMC genomics. 17, 222
Zoltner, M., Ng, W. M., Money, J. J., Fyfe, P. K., Kneuper, H., Palmer, T. and Hunter, W. N. (2016) EssC: domain structures inform on the elusive translocation channel in the Type VII secretion system. The Biochemical journal. 473, 1941-1952
Browning, D. F., Bavro, V. N., Mason, J. L., Sevastsyanovich, Y. R., Rossiter, A. E., Jeeves, M., Wells, T. J., Knowles, T. J., Cunningham, A. F., Donald, J. W., Palmer, T., Overduin, M. and Henderson, I. R. (2015) Cross-species chimeras reveal BamA POTRA and beta-barrel domains must be fine-tuned for efficient OMP insertion. Mol Microbiol. 97, 646-659
Cleon, F., Habersetzer, J., Alcock, F., Kneuper, H., Stansfeld, P. J., Basit, H., Wallace, M. I., Berks, B. C. and Palmer, T. (2015) The TatC component of the twin-arginine protein translocase functions as an obligate oligomer. Mol Microbiol. 98, 111-129
Kelly, C. L., Pinske, C., Murphy, B. J., Parkin, A., Armstrong, F., Palmer, T. and Sargent, F. (2015) Integration of an [FeFe]-hydrogenase into the anaerobic metabolism of. Biotechnology reports. 8, 94-104
McDowall, J. S., Hjersing, M. C., Palmer, T. and Sargent, F. (2015) Dissection and engineering of the Escherichia coli formate hydrogenlyase complex. FEBS Lett. 589, 3141-3147
Dow, J. M., Grahl, S., Ward, R., Evans, R., Byron, O., Norman, D. G., Palmer, T. and Sargent, F. (2014) Characterization of a periplasmic nitrate reductase in complex with its biosynthetic chaperone. The FEBS journal. 281, 246-260
Hamilton, J. J., Marlow, V. L., Owen, R. A., Costa Mde, A., Guo, M., Buchanan, G., Chandra, G., Trost, M., Coulthurst, S. J., Palmer, T., Stanley-Wall, N. R. and Sargent, F. (2014) A holin and an endopeptidase are essential for chitinolytic protein secretion in Serratia marcescens. J Cell Biol. 207, 615-626
Hopkins, A., Buchanan, G. and Palmer, T. (2014) Role of the twin arginine protein transport pathway in the assembly of the Streptomyces coelicolor cytochrome bc1 complex. J Bacteriol. 196, 50-59
Kneuper, H., Cao, Z. P., Twomey, K. B., Zoltner, M., Jager, F., Cargill, J. S., Chalmers, J., van der Kooi-Pol, M. M., van Dijl, J. M., Ryan, R. P., Hunter, W. N. and Palmer, T. (2014) Heterogeneity in ess transcriptional organization and variable contribution of the Ess/Type VII protein secretion system to virulence across closely related Staphylocccus aureus strains. Mol Microbiol. 93, 928-943
McDowall, J. S., Murphy, B. J., Haumann, M., Palmer, T., Armstrong, F. A. and Sargent, F. (2014) Bacterial formate hydrogenlyase complex. Proc Natl Acad Sci U S A. 111, E3948-3956
Alcock, F., Baker, M. A., 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 U S A. 110, E3650-3659
Bowman, L., Palmer, T. and Sargent, F. (2013) A regulatory domain controls the transport activity of a twin-arginine signal peptide. FEBS Lett. 587, 3365-3370
Dow, J. M., Gabel, F., Sargent, F. and Palmer, T. (2013) Characterization of a pre-export enzyme-chaperone complex on the twin-arginine transport pathway. Biochem J. 452, 57-66
Fyans, J. K., Bignell, D., Loria, R., Toth, I. and Palmer, T. (2013) The ESX/type VII secretion system modulates development, but not virulence, of the plant pathogen Streptomyces scabies. Molecular plant pathology. 14, 119-130
James, M. J., Coulthurst, S. J., Palmer, T. and Sargent, F. (2013) Signal peptide etiquette during assembly of a complex respiratory enzyme. Mol Microbiol. 90, 400-414
Sargent, F., Davidson, F. A., Kelly, C. L., Binny, R., Christodoulides, N., Gibson, D., Johansson, E., Kozyrska, K., Lado, L. L., Maccallum, J., Montague, R., Ortmann, B., Owen, R., Coulthurst, S. J., Dupuy, L., Prescott, A. R. and Palmer, T. (2013) A synthetic system for expression of components of a bacterial microcompartment. Microbiology. 159, 2427-2436
Zoltner, M., Fyfe, P. K., Palmer, T. and Hunter, W. N. (2013) Characterization of Staphylococcus aureus EssB, an integral membrane component of the Type VII secretion system: atomic resolution crystal structure of the cytoplasmic segment. Biochem J. 449, 469-477
Zoltner, M., Norman, D. G., Fyfe, P. K., El Mkami, H., Palmer, T. and Hunter, W. N. (2013) The architecture of EssB, an integral membrane component of the type VII secretion system. Structure. 21, 595-603
Fritsch, M. J., Krehenbrink, M., Tarry, M. J., Berks, B. C. and Palmer, T. (2012) Processing by rhomboid protease is required for Providencia stuartii TatA to interact with TatC and to form functional homo-oligomeric complexes. Mol Microbiol. 84, 1108-1123
Keller, R., de Keyzer, J., Driessen, A. J. and Palmer, T. (2012) Co-operation between different targeting pathways during integration of a membrane protein. J Cell Biol. 199, 303-315
Kneuper, H., Maldonado, B., Jager, F., Krehenbrink, M., Buchanan, G., Keller, R., Muller, M., Berks, B. C. and Palmer, T. (2012) Molecular dissection of TatC defines critical regions essential for protein transport and a TatB-TatC contact site. Mol Microbiol. 85, 945-961
Koch, S., Fritsch, M. J., Buchanan, G. and Palmer, T. (2012) Escherichia coli TatA and TatB proteins have N-out, C-in topology in intact cells. J Biol Chem. 287, 14420-14431
Palmer, T. and Berks, B. C. (2012) The twin-arginine translocation (Tat) protein export pathway. Nature reviews. Microbiology. 10, 483-496
Parkin, A., Bowman, L., Roessler, M. M., Davies, R. A., Palmer, T., Armstrong, F. A. and Sargent, F. (2012) How Salmonella oxidises H(2) under aerobic conditions. FEBS Lett. 586, 536-544
Rollauer, S. E., Tarry, M. J., Graham, J. E., Jaaskelainen, M., Jager, F., Johnson, S., Krehenbrink, M., Liu, S. M., Lukey, M. J., Marcoux, J., McDowell, M. A., Rodriguez, F., Roversi, P., Stansfeld, P. J., Robinson, C. V., Sansom, M. S., Palmer, T., Hogbom, 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
Willemse, J., Ruban-Osmialowska, B., Widdick, D., Celler, K., Hutchings, M. I., van Wezel, G. P. and Palmer, T. (2012) Dynamic localization of Tat protein transport machinery components in Streptomyces coelicolor. J Bacteriol. 194, 6272-6281