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Shigella flexneri Spa15 crystal structure verified in solution by double electron electron resonance
James E D Lillington1, Janet E Lovett, Steven Johnson
1Inorganic Chemistry Laboratory, University of Oxford, OX1 3QR, UK.
Journal of Molecular Biology
|November 16, 2010
Summary
Shigella flexneri Spa15 chaperone binds effector IpgB1 differently than its Salmonella counterpart. Structural and distance data reveal Spa15
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- Shigella flexneri utilizes a type 3 secretion system (T3SS) for pathogenesis.
- Spa15 is a T3SS chaperone that stabilizes effector proteins before secretion.
- IpgB1 is a T3SS effector that mimics human Rho guanosine triphosphatase RhoG.
Purpose of the Study:
- To investigate the structural and binding characteristics of Shigella flexneri Spa15.
- To determine the interaction mode between Spa15 and its effector IpgB1.
- To compare the Spa15:IpgB1 complex with homologous chaperone:effector interactions.
Main Methods:
- Double electron electron resonance (DEER) spectroscopy to measure distances between spin labels.
- X-ray crystallography to determine the crystal structure of spin-labeled Spa15.
- Biochemical analysis of chaperone:effector complex formation.
Main Results:
- DEER experiments provided distance information on Spa15 and its complex with IpgB1.
- Crystal structure revealed spin labels on Spa15 are located in hydrophobic pockets.
- IpgB1 does not bind to Spa15 in the same manner as observed in Salmonella sp. InvB:SipA complex.
Conclusions:
- Spa15 exhibits unique structural features and binding properties.
- The interaction between Spa15 and IpgB1 is distinct from other characterized chaperone:effector pairs.
- This study provides insights into the specificity of T3SS chaperone:effector recognition.
