Biochemical Analysis of Salmonella Type III Secretion System Effector Protein SopB
Berryman, Meghan A.
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Salmonella is a bacterial pathogen responsible for food-born gastroenteritis and typhoid fever in humans. The pathogen modulates pre-established signaling cascades within the host cell using its own macromolecular protein structure, Type III Secretion System (T3SS), that sits within the layers of the bacterial cell membrane and penetrates the host cell by creating a pore in its surface. This allows Salmonella to inject virulence proteins, called effector proteins, directly into the host cell. Inositol phosphate phosphatase SopB is one of the key effector proteins. Through indirect stimulus of guanosine triphosphatases (GTPases) Cdc42 and Rac, SopB triggers actin cytoskeleton rearrangements and membrane ruffling, cellular effects characteristic of Salmonella infection. Previous scientists have been unsuccessful in attempts to purify and stabilize protein SopB for crystallographic analysis. This study modified the protocol for purification. These modifications allowed for the protein to spend as little time as possible in unstable environments, such as extreme temperature change, while the process of purification was underway. This approach was successful in purifying and concentrating SopB and Cdc42 protein complex for use in recrystal study.