Poster Presentation The 43rd Lorne Conference on Protein Structure and Function 2018

The influence of mortise-tenon joints on OmpF stability (#204)

Jiansi Long 1 , Matthew D Johnson 1 , Xiaojun Yuan 1 , Denisse Leyton 1 2
  1. Research School of Biology, Australian National University, Acton, ACT, Australia
  2. Medical School, Australian National University, Acton, ACT, Australia

Outer membrane β-proteins (OMPs) serve many essential functions to bacterial cells. OMPs are distinguished from inner membrane proteins by their β-barrel structure. OmpF is a trimeric general porin that allows the non-specific diffusion of small hydrophilic solutes into the bacterial cells, and is also the receptor and translocator of colicin. However, the precise mechanism by which OmpF attains its native trimeric fold in cellular and artificial membranes is unknown. Like other general porins, OmpF is a highly studied protein for use as a nanopore in current nanopore biotechnology research because of its well-studied structure and function. However, the main limitations restricting the application of OmpF in nanomedicine, biosensing, and bioelectronics are its high molecular weight and its trimer-dependent stability. Recent studies identified glycine-aromatic pairings between two adjacent β-strands called mortise-tenon joints in OmpF that have been shown to be required for stability of OMPs outside of the general porin family. Given their proven role in stabilizing OMPs in other OMP families, and high prevalence in the remaining major OMP families, it is hypothesized that mortise-tenon joints are a universal OMP stabilizing mechanism. Therefore, the research question tested in this project is whether mortise-tenon joints are required to stabilize OmpF and if they are necessary for trimerization. Using biochemical and biophysical analyses on in vitro refolded OmpF, we have assessed the effects of both the deletion and addition of mortise-tenon joints on OmpF stability and trimerization. This work demonstrates that mortise-tenon joints could play a role in OmpF stability and trimer assembly, but these effects depend on their positioning in the OmpF β-barrel.