Structural and biophysical characterisation of the translocation and assembly module (TAM) complex from Escherichia coli

Josts, Inokentijs (2014) Structural and biophysical characterisation of the translocation and assembly module (TAM) complex from Escherichia coli. PhD thesis, University of Glasgow.

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Bacterial proteins destined to function extracellularly must efficiently cross two layers of membrane covering the cells. To do so, numerous transporter systems are employed to ensure the delivery of these proteins to their final destination in their fully functional state. Autotransporters are outer membrane bound proteins that act in the extracellular milleau of the cells and act as virulence factors mediating contact with the host and the manipulation of host defence. The translocation assembly module (TAM complex) is a cell envelope spanning complex produced by Gram-negative bacteria that facilitates efficient secretion of autotransporters across the outer membrane. This complex consists of the outer membrane protein TamA, a member of the Omp85 superfamily of proteins, which consists of an integral membrane β-barrel domain and three soluble periplasmic polypeptide transport (POTRA) domains and the large inner membrane anchored protein TamB.

This work examines the interactions between TamA and TamB which are mediated through interaction of the central polypeptide transport domain of TamA and the C-terminal region of the DUF490 domain of TamB. In addition, it is also demonstrated that TamB forms a complex with the unfolded passenger domain of the substrate autotransporter Ag43 and that the TamA and Ag43 binding epitopes of TamB are overlapping but not identical. These data suggest that TamB acts as a chaperone, delivering autotransporter passenger domains to the TamA POTRA domains, which interact transiently with the Ag43 passenger domain. These transient interactions presumably act to guide the unfolded polypeptide into the TamA barrel for efficient secretion across the outer membrane.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Publications:

Mccaughey, L. C. et al. (2014) Lectin-like bacteriocins from Pseudomonas spp. utilise D-rhamnose containing lipopolysaccharide as a cellular receptor. PLoS Pathogens, 10(2), e1003898. (doi:10.1371/journal.ppat.1003898) (CC BY 4.0)

Grinter, R., Josts, I., Zeth, K., Roszak, A. W., McCaughey, L. C., Cogdell, R. J., Milner, J. J., Kelly, S. M.,Byron, O., and Walker, D. (2014) Structure of the atypical bacteriocin pectocin M2 implies a novel mechanism of protein uptake. Molecular Microbiology, 93(2), pp. 234-246. (doi:10.1111/mmi.12655) (CC BY 3.0)

Josts, I., Grinter, R., Kelly, S. M., Mosbahi, K., Roszak, A., Cogdell, R., Smith, B. O., Byron, O., and Walker, D.(2014) Recombinant expression, purification, crystallization and preliminary X-ray diffraction analysis of the C-terminal DUF490963–1138 domain of TamB from Escherichia coli. Acta Crystallographica. Section F: Structural Biology Communications, 70(9), pp. 1272-1275. (doi:10.1107/S2053230X14017403)
Keywords: TamA, TamB, Ag43, autotransporter, BAM, Omp85, outer membrane.
Subjects: Q Science > QR Microbiology
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
Supervisor's Name: Walker, Dr. Daniel and Byron, Dr. Olwyn
Date of Award: 2014
Depositing User: Mrs Marie Cairney
Unique ID: glathesis:2014-6509
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 Jun 2015 09:50
Last Modified: 29 May 2017 12:14

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