Team:UCLA/Project

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Revision as of 20:48, 26 September 2013

Overall project

In-Vitro Immune System

Diversity is an important feature of biological systems, and it can be harnessed to serve as a useful tool in synthetic biology.

Many organisms have molecular mechanisms to generate diversity at the DNA level in order to accelerate evolution. This is true in particular with host/pathogen interactions, where the host must mutate to protect itself from the pathogen and the pathogen mutates to evade host defenses. One important example of such diversity generating mechanisms is found in the Bordetella bacteriophage BPP-1. Bordetella is a genus of bacteria that can infect the mammalian respiratory tract, causing diseases such as pertussis (whooping cough). The infectious cycle of the Bordetella bacteria involves a switch between a non-infectious and an infectious stage with different virulence factors and surface receptors expressed. Interactions between bacteria surface receptors and phage tail fiber proteins are extremely specific. The tip of each virus tail-fiber is a protein called the major tropism-determinant protein (Mtd), which binds to the hosts’ surface and allows the phage to infect it. In order to successfully infect both phases of the host bacteria, the BPP-1 phage uses a complex genetic mechanism to generate diversity at the host-recognition site of the Mtd protein.

Though the general structure of the Mtd protein is constant and very stable, its active ends are extremely variable. Each phage produces a slightly different structural variant of the protein, with the hope that at least one phage can successfully bind to the host and infect it - akin to the way our immune system produces numerous variants of antibodies so that at least one can bind to the antigen of interest.

[you should put some background info here about how people have done phage display with this system in the past] Our team hopes to develop a fully in-vitro system to express and select for mtd variants of interest.

We plan on first generating a diverse DNA library of the mtd gene, then using mRNA-display to detect and screen for the variants of the protein that can bind to a selected target. In our case, the target will be the surface of E. Coli bacterial cells.

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 <h4>The Virus</h4>
-The BPP-1 virus is a bacteriophage belonging to the <i>Podoviridae</i> family. It has an icosahedral head with T=7 symmetry, and a short, noncontractile tail with six tail “spikes” attached to tail fibers. At the end of these tail fibers are Major Tropism Determinant (Mtd) proteins, which bind to the pertactin proteins expressed on the surface of <i>Bordetella</i>. The Mtd protein does not display high affinity for pertactin, but the multiple Mtd proteins possessed by each phage particle coupled with the flexibility of the tail fibers allow BPP-1 as a whole to have high avidity for its host. Following infection, the virus is lytic, and destroys the bacterial host to release more copies of itself.
+The BPP-1 virus is a bacteriophage belonging to the <i>Podoviridae</i> family. It has an icosahedral head with T=7 symmetry, and a short, noncontractile tail with six tail “spikes” attached to tail fibers. At the end of these tail fibers are major tropism determinant (Mtd) proteins, which bind to the pertactin proteins expressed on the surface of <i>Bordetella</i>. The Mtd protein does not display high affinity for pertactin, but the multiple Mtd proteins possessed by each phage particle coupled with the flexibility of the tail fibers allow BPP-1 as a whole to have high avidity for its host. Following infection, the virus is lytic, and destroys the bacterial host to release more copies of itself.
 ==mRNA Display==