Molecular Playground/ClyA: Difference between revisions

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Bib Yang, Monifa Fahie, Michal Harel

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+<Structure load='1QOY' size='350' frame='true' align='right' caption='ClyA complex with sulfate (PDB code [[1qoy]]).' scene='Insert optional scene name here' />
+==Introduction==
-==About this Structure==
+Pore-forming toxins (PFTs) are virulence factors secreted by pathogenic organisms.  These are proteins that form transmembrane channels on target cell membranes.  They cause cell death by making the cell membrane permeable, leading to osmotic imbalance and lysis.  There are two classes of PFTs based on their secondary structure, alpha-PFTs and beta-PFTs.  '''Cytolysin A (ClyA)''' is an alpha-PFT and is secreted by ''Salmonella'', ''Shigella'' and ''E. coli'' strains.
-[[Image:ClyA-monomer2.png]]
-Figure 1. The soluble ClyA monomer, [[1QOY]], rendered in PyMol.
+==About Cytolysin A==
-[[1QOY]] in Figure 1 above is a monomer from the dodecameric pore-forming toxin (PFT) from [http://en.wikipedia.org/wiki/Escherichia_coli ''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.
+<scene name='57/571278/Clya_monomer/2'>ClyA monomer in its inactive form</scene>
-Its crystal structure, [[2WCD]], as shown in Figure 2 below, reveals a dodecamer. Larger [http://pubs.acs.org/doi/abs/10.1021/ja4053398 pores] have been isolated, as well.
-[[Image:ClyA.png]] [[Image:ClyA-protomer.png]]
+[[1qoy]] is a 34 kDa monomer from [http://en.wikipedia.org/wiki/Escherichia_coli ''Escherichia coli''] (''E. coli''). It is an alpha-PFT comprised of four alpha helicies, a smaller fifth alpha helix, and a <B><font color="purple">beta tongue</font></B>. The <B><font color="blue">N-terminus</font></B> and the <B><font color="red">C-terminus</font></B> are highlighted. 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, possessing the ability to lyse the host cell.
-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.
+<scene name='57/571278/Clya_protomer/1'>ClyA protomer</scene>
-<scene name='57/571278/Clya_oligomer/1'>The oligomeric form of ClyA</scene>
+The protomer of ClyA reveals slight differences between the monomer and protomer (from the dodecameric oligomer). The major conformational changes between the monomer and the protomer are the positions of the <B><font color="blue">N-terminal helix</font></B> and the <B><font color="purple">beta-tongue</font></B>. 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.
+<scene name='57/571278/Clya_oligomer/3'>The oligomeric form of ClyA with a protomer highlighted in crimson</scene>
+Its crystal structure, [[2WCD]], reveals a dodecamer. Larger [http://pubs.acs.org/doi/abs/10.1021/ja4053398 pores] have been isolated, as well. A few research endeavors involving ClyA include using [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2839435/ ClyA as part of cancer therapy], as well as a [http://www.nature.com/ncomms/2013/130912/ncomms3415/full/ncomms3415.html DNA delivery vehicle].
 ==Research on ClyA at UMass Amherst==
-The Chen Lab, in collaboration with the Heuck lab, recently published a paper on [http://www.jbc.org/content/288/43/31042.short, ClyA] assembly. Currently, we are investigating electroosmotic flow and electrophoretic force, the forces that influence polymer translocation through ClyA.
+The [http://www.chem.umass.edu/~chenlab/index.HTML, Chen Lab] recently published a paper on [http://www.jbc.org/content/288/43/31042.short, ClyA] non-classical assembly. We use a technique commonly used for nanopore sensing called electrophysiology, which allows us to measure the ionic current through the ClyA nanopore.
+Current ClyA projects focus on 3 main areas:
+ClyA non-classical assembly and attack
+ClyA engineered for cancer therapy
+Studies of [http://en.wikipedia.org/wiki/Electro-osmosis, electro-osmosis] using ClyA nanopore
+==References==
+.	Wallace, a J. et al. E. coli hemolysin E (HlyE, ClyA, SheA): X-ray crystal structure of the toxin and observation of membrane pores by electron microscopy. Cell 100, 265–76 (2000).
+.	Atkins, a et al. Structure-function relationships of a novel bacterial toxin, hemolysin E. The role of alpha G. J. Biol. Chem. 275, 41150–5 (2000).
+.	Mueller, M., Grauschopf, U., Maier, T., Glockshuber, R. & Ban, N. The structure of a cytolytic alpha-helical toxin pore reveals its assembly mechanism. Nature 459, 726–30 (2009).
+.	Fahie, M. et al. A non-classical assembly pathway of Escherichia coli pore-forming toxin cytolysin A. J. Biol. Chem. 288, 31042–51 (2013).