Molecular Playground/ClyA
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About this StructureAbout this Structure
Figure 1. The soluble ClyA monomer, 1QOY, rendered in PyMol. 1QOY in Figure 1 above is a monomer from the dodecameric pore-forming toxin (PFT) from Escherichia coli. It is a 34kDa protein comprised of four alpha helicies, a smaller fifth alpha helix, and a beta tongue. ClyA has been shown to form pores through a non-classical assembly pathway, excreted in oligomeric form in outer-membrane vesicles (OMV) as pre-pores. Only until ClyA reaches the target host membrane does it form the dodecameric PFT with hemolytic activity. Its crystal structure, 2WCD, as shown in Figure 2 below, reveals a dodecamer. Larger pores have been isolated, as well.
File:ClyA.png File:ClyA-protomer.png Figure 2. The dodecameric ClyA crystal structure revealing its lumen (left), rendered in PyMol. The protomer of ClyA is on the right.
The protomer of ClyA, shown in Figure 2 on the right, reveals slight differences between the monomer and protomer. The major conformational changes between the monomer and the protomer are the positions of the N-terminal helix and the beta-tongue. As ClyA oligomerizes and forms a pore, the N-terminal helix swings to the opposite side of the molecule while the beta-tongue changes its conformation and turns into an alpha-helix that interacts with the lipid bilayer.
Research on ClyA at UMass AmherstResearch on ClyA at UMass Amherst
The Chen Lab, in collaboration with the Heuck lab, recently published a paper on ClyA assembly. Currently, we are investigating electroosmotic flow and electrophoretic force, the forces that influence polymer translocation through ClyA.