Poster Presentation The 45th Lorne Conference on Protein Structure and Function 2020

Identification of novel periplasmic chaperones involved in the biogenesis of the bacterial Translocase Assembly Machinery – TAM  (#400)

Chaille T Webb 1 , Trevor Lithgow 1
  1. Infection & Immunity Program, Biomedicine Discovery Institute , Department of Microbiology, Monash University, Melbourne, VIC, Australia

With around 20% of the E. coli proteome destined for the cell envelope, quality control mechanisms must be implemented by the cell, to ensure the effective and correct folding of proteins destined for the inner and outer membranes. These are comprised largely of chaperones and proteases that reside within the periplasm, several of which have been well characterised including SurA, Skp, and DegP just to name a few 1. However, there are more and more cases whereby specific proteins utilise a specific chaperone to support their biogenesis assembly pathway.

The translocase assembly machinery or TAM is a protein complex spanning the bacterial cell envelope and is involved in the assembly of outer membrane secretion systems. It is composed of the outer membrane protein, TamA, that adopts a b-barrel fold within the membrane and also contains a periplasmic soluble domain that interacts with its partner protein, TamB. Much less is known about TamB, suffice to say it is a very large (150kDa) periplasmic protein that is anchored to the inner membrane via its N-terminus 2,3.  To identify novel chaperones involved in TAM biogenesis we have performed transcriptomics of E. coli  during the overexpression of TamA and TamB.  In doing so we have identified several candidate proteins that may be implicated in TAM assembly. Here we biochemically assess some of these candidates to further understand their role during membrane protein folding.

  1. Goemans, C., Denoncin, K. & Collet, J. F. Folding mechanisms of periplasmic proteins. Biochim Biophys Acta 1843, 1517-1528, doi:10.1016/j.bbamcr.2013.10.014 (2014).
  2. Selkrig, J. et al. Discovery of an archetypal protein transport system in bacterial outer membranes. Nat Struct Mol Biol 19, 506-510, S501, doi:10.1038/nsmb.2261 (2012).
  3. Stubenrauch, C. et al. Effective assembly of fimbriae in Escherichia coli depends on the translocation assembly module nanomachine. Nat Microbiol 1, 16064, doi:10.1038/nmicrobiol.2016.64 (2016).