3zqb

From Proteopedia

PrgI-SipD from Salmonella typhimurium

Structural highlights

3zqb is a 2 chain structure with sequence from Salmonella enterica subsp. enterica serovar Typhimurium str. SL1344. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 2.4Å
Ligands:
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

SIPD_SALTY Required for translocation of effector proteins via the type III secretion system SPI-1, which is essential for an efficient bacterial internalization. Probably acts by modulating the secretion of SipA, SipB, and SipC.^[1] ^[2] PRGI_SALTY Required for invasion of epithelial cells.

Publication Abstract from PubMed

Many infectious gram-negative bacteria, including Salmonella typhimurium, require a Type Three Secretion System (T3SS) to translocate virulence factors into host cells. The T3SS consists of a membrane protein complex and an extracellular needle together that form a continuous channel. Regulated secretion of virulence factors requires the presence of SipD at the T3SS needle tip in S. typhimurium. Here we report three-dimensional structures of individual SipD, SipD in fusion with the needle subunit PrgI, and of SipD:PrgI in complex with the bile salt, deoxycholate. Assembly of the complex involves major conformational changes in both SipD and PrgI. This rearrangement is mediated via a pi bulge in the central SipD helix and is stabilized by conserved amino acids that may allow for specificity in the assembly and composition of the tip proteins. Five copies each of the needle subunit PrgI and SipD form the T3SS needle tip complex. Using surface plasmon resonance spectroscopy and crystal structure analysis we found that the T3SS needle tip complex binds deoxycholate with micromolar affinity via a cleft formed at the SipD:PrgI interface. In the structure-based three-dimensional model of the T3SS needle tip, the bound deoxycholate faces the host membrane. Recently, binding of SipD with bile salts present in the gut was shown to impede bacterial infection. Binding of bile salts to the SipD:PrgI interface in this particular arrangement may thus inhibit the T3SS function. The structures presented in this study provide insight into the open state of the T3SS needle tip. Our findings present the atomic details of the T3SS arrangement occurring at the pathogen-host interface.

Crystal structure of PrgI-SipD: insight into a secretion competent state of the type three secretion system needle tip and its interaction with host ligands.,Lunelli M, Hurwitz R, Lambers J, Kolbe M PLoS Pathog. 2011 Aug;7(8):e1002163. Epub 2011 Aug 4. PMID:21829362^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Kaniga K, Trollinger D, Galan JE. Identification of two targets of the type III protein secretion system encoded by the inv and spa loci of Salmonella typhimurium that have homology to the Shigella IpaD and IpaA proteins. J Bacteriol. 1995 Dec;177(24):7078-85. PMID:8522512
↑ Collazo CM, Galan JE. The invasion-associated type III system of Salmonella typhimurium directs the translocation of Sip proteins into the host cell. Mol Microbiol. 1997 May;24(4):747-56. PMID:9194702
↑ Lunelli M, Hurwitz R, Lambers J, Kolbe M. Crystal structure of PrgI-SipD: insight into a secretion competent state of the type three secretion system needle tip and its interaction with host ligands. PLoS Pathog. 2011 Aug;7(8):e1002163. Epub 2011 Aug 4. PMID:21829362 doi:10.1371/journal.ppat.1002163