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Title: Identification of the bile salt binding site on ipad from Shigella flexneri and the influence of ligand binding on IpaD structure

Abstract

Type III secretion (TTS) is an essential virulence factor for Shigella flexneri, the causative agent of shigellosis. The Shigella TTS apparatus (TTSA) is an elegant nano-machine that is composed of a basal body, an external needle to deliver effectors into human cells, and a needle tip complex that controls secretion activation. IpaD is at the tip of the nascent TTSA needle where it controls the first step of TTS activation. The bile salt deoxycholate (DOC) binds to IpaD to induce recruitment of the translocator protein IpaB into the maturing tip complex. We recently used spectroscopic analyses to show that IpaD undergoes a structural rearrangement that accompanies binding to DOC. Here, we report a crystal structure of IpaD with DOC bound and test the importance of the residues that make up the DOC binding pocket on IpaD function. IpaD binds DOC at the interface between helices {alpha}3 and {alpha}7, with concomitant movement in the orientation of helix {alpha}7 relative to its position in unbound IpaD. When the IpaD residues involved in DOC binding are mutated, some are found to lead to altered invasion and secretion phenotypes. These findings suggest that adoption of a DOC-bound structural state for IpaD primes the Shigellamore » TTSA for contact with host cells. The data presented here and in the studies leading up to this work provide the foundation for developing a model of the first step in Shigella TTS activation.« less

Authors:
; ; ; ; ; ; ;  [1];  [2]
  1. (UMKC)
  2. (
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
NIHOTHER U.S. STATES
OSTI Identifier:
1040646
Resource Type:
Journal Article
Journal Name:
Proteins
Additional Journal Information:
Journal Volume: 80; Journal Issue: (3) ; 03, 2012; Journal ID: ISSN 0887-3585
Country of Publication:
United States
Language:
ENGLISH
Subject:
59 BASIC BIOLOGICAL SCIENCES; 60 APPLIED LIFE SCIENCES; ANIMAL CELLS; ANTIGENS; BILE; CRYSTAL STRUCTURE; ORIENTATION; PLASMIDS; PROTEINS; RESIDUES; SECRETION; SHIGELLA; VIRULENCE

Citation Formats

Barta, Michael L., Guragain, Manita, Adam, Philip, Dickenson, Nicholas E., Patil, Mrinalini, Geisbrecht, Brian V., Picking, Wendy L., Picking, William D., and OKLU). Identification of the bile salt binding site on ipad from Shigella flexneri and the influence of ligand binding on IpaD structure. United States: N. p., 2012. Web. doi:10.1002/prot.23251.
Barta, Michael L., Guragain, Manita, Adam, Philip, Dickenson, Nicholas E., Patil, Mrinalini, Geisbrecht, Brian V., Picking, Wendy L., Picking, William D., & OKLU). Identification of the bile salt binding site on ipad from Shigella flexneri and the influence of ligand binding on IpaD structure. United States. doi:10.1002/prot.23251.
Barta, Michael L., Guragain, Manita, Adam, Philip, Dickenson, Nicholas E., Patil, Mrinalini, Geisbrecht, Brian V., Picking, Wendy L., Picking, William D., and OKLU). Thu . "Identification of the bile salt binding site on ipad from Shigella flexneri and the influence of ligand binding on IpaD structure". United States. doi:10.1002/prot.23251.
@article{osti_1040646,
title = {Identification of the bile salt binding site on ipad from Shigella flexneri and the influence of ligand binding on IpaD structure},
author = {Barta, Michael L. and Guragain, Manita and Adam, Philip and Dickenson, Nicholas E. and Patil, Mrinalini and Geisbrecht, Brian V. and Picking, Wendy L. and Picking, William D. and OKLU)},
abstractNote = {Type III secretion (TTS) is an essential virulence factor for Shigella flexneri, the causative agent of shigellosis. The Shigella TTS apparatus (TTSA) is an elegant nano-machine that is composed of a basal body, an external needle to deliver effectors into human cells, and a needle tip complex that controls secretion activation. IpaD is at the tip of the nascent TTSA needle where it controls the first step of TTS activation. The bile salt deoxycholate (DOC) binds to IpaD to induce recruitment of the translocator protein IpaB into the maturing tip complex. We recently used spectroscopic analyses to show that IpaD undergoes a structural rearrangement that accompanies binding to DOC. Here, we report a crystal structure of IpaD with DOC bound and test the importance of the residues that make up the DOC binding pocket on IpaD function. IpaD binds DOC at the interface between helices {alpha}3 and {alpha}7, with concomitant movement in the orientation of helix {alpha}7 relative to its position in unbound IpaD. When the IpaD residues involved in DOC binding are mutated, some are found to lead to altered invasion and secretion phenotypes. These findings suggest that adoption of a DOC-bound structural state for IpaD primes the Shigella TTSA for contact with host cells. The data presented here and in the studies leading up to this work provide the foundation for developing a model of the first step in Shigella TTS activation.},
doi = {10.1002/prot.23251},
journal = {Proteins},
issn = {0887-3585},
number = (3) ; 03, 2012,
volume = 80,
place = {United States},
year = {2012},
month = {10}
}