The role of the TAM in beta-barrel biogenesis

Research output: Contribution to conferencePoster


The biogenesis of the outer membrane of bacterial pathogens is a significant pathway in bacterial cell biology. Outer membrane protein assembly is mediated by the beta-barrel assembly machinery, the core component of which is the BAM complex. The translocation and assembly module (TAM) is also capable of assembling outer membrane proteins, but its function has remained enigmatic. To determine the function of the TAM, a pulse chase assay was developed to characterise the specific contributions of the TAM and the BAM complex for a range of outer membrane protein substrates.
Using this technique, eight fimbrial ushers were assigned to the TAM-dependent category of outer membrane proteins. Of these, the usher protein FimD, from which Type I fimbriae emanate, was found to contain an unusual extracellular loop that was readily proteolytically degraded on addition of exogenous proteinase K. Because distinct proteolytic fragmentation "fingerprints" were generated depending on the presence or absence of the TAM, this provided a powerful tool to dissect the contribution of the TAM toward FimD biogenesis. The TAM was thereby demonstrated to initiate β-barrel assembly from the C-terminal end of the substrate. While the BAM complex was also capable of assembling FimD, it was significantly less efficient because it initiated β-barrel assembly from a central region of the protein. The assay has now been adapted to study a diverse range of outer membrane proteins, leading to the conclusion that the TAM is generally important for the assembly of outer membrane proteins with complicated transmembrane topologies.
Original languageEnglish
Publication statusPublished - 7 Feb 2017
EventLorne Conference on Protein Structure and Function 2017 - Mantra Resort, Lorne, Australia
Duration: 5 Feb 20179 Feb 2017
Conference number: 42nd


ConferenceLorne Conference on Protein Structure and Function 2017

Cite this

Stubenrauch, C. J. (2017). The role of the TAM in beta-barrel biogenesis. Poster session presented at Lorne Conference on Protein Structure and Function 2017, Lorne, Australia.