NMR Model of PrgI-SipD Interaction and its Implications in the Needle-Tip Assembly of the Salmonella Type III Secretion System

Rathinavelan, T and Tejero, M L and Lefebre, M and Chatterjee, S and McShan, A C and Guo, D C and Tang, C and Galan, J E and De Guzman, R N (2014) NMR Model of PrgI-SipD Interaction and its Implications in the Needle-Tip Assembly of the Salmonella Type III Secretion System. Journal of Molecular Biology, 426 (16). pp. 2958-2969. ISSN 0022-2836

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Abstract

Salmonella and other pathogenic bacteria use the type III secretion system (T3SS) to inject virulence proteins into human cells to initiate infections. The structural component of the T3SS contains a needle and a needle tip. The needle is assembled from PrgI needle protomers and the needle tip is capped with several copies of the SipD tip protein. How a tip protein docks on the needle is unclear. A crystal structure of a PrgI–SipD fusion protein docked on the PrgI needle results in steric clash of SipD at the needle tip when modeled on the recent atomic structure of the needle. Thus, there is currently no good model of how SipD is docked on the PrgI needle tip. Previously, we showed by NMR paramagnetic relaxation enhancement (PRE) methods that a specific region in the SipD coiled coil is the binding site for PrgI. Others have hypothesized that a domain of the tip protein—the N-terminal α-helical hairpin—has to swing away during the assembly of the needle apparatus. Here, we show by PRE methods that a truncated form of SipD lacking the α-helical hairpin domain binds more tightly to PrgI. Further, PRE-based structure calculations revealed multiple PrgI binding sites on the SipD coiled coil. Our PRE results together with the recent NMR-derived atomic structure of the Salmonella needle suggest a possible model of how SipD might dock at the PrgI needle tip. SipD and PrgI are conserved in other bacterial T3SSs; thus, our results have wider implication in understanding other needle-tip complexes

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IITH Creators:
IITH CreatorsORCiD
Item Type: Article
Additional Information: We are grateful to Carey Johnson and Mark Richter (University of Kansas) for helpful discussion on the fluorescence spectroscopy part. NOTE: Dr. Thenmalarchelvi Rathinavelan - Present address: IIT Hyderabad
Uncontrolled Keywords: Salmonella; type III secretion; SipD; PrgI; NMR
Subjects: Others > Biotechnology
Divisions: Department of Biotechnology
Depositing User: Library Staff
Date Deposited: 05 Mar 2015 06:25
Last Modified: 05 Mar 2015 06:25
URI: http://raiith.iith.ac.in/id/eprint/1371
Publisher URL: http://dx.doi.org/10.1016/j.jmb.2014.06.009
OA policy: http://www.sherpa.ac.uk/romeo/issn/0022-2836/
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