Structure of AcrH-AopB Chaperone-Translocator Complex Reveals a Role for Membrane Hairpins in Type III Secretion System Translocon Assembly

Van Sang Nguyen, Chacko Jobichen, Kang Wei Tan, Yih Wan Tan, Siew Leong Chan, Karthik Ramesh, Yongming Yuan, Yunhan Hong, Jayaraman Seetharaman, Ka Yin Leung, J. Sivaraman, Yu Keung Mok*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Type III secretion systems (T3SSs) are adopted by pathogenic bacteria for the transport of effector proteins into host cells through the translocon pore composed of major and minor translocator proteins. Both translocators require a dedicated chaperone for solubility. Despite tremendous efforts in the past, structural information regarding the chaperone-translocator complex and the topology of the translocon pore have remained elusive. Here, we report the crystal structure of the major translocator, AopB, from Aeromonas hydrophila AH-1 in complex with its chaperone, AcrH. Overall, the structure revealed unique interactions between the various interfaces of AopB and AcrH, with the N-terminal "molecular anchor" of AopB crossing into the "N-terminal arm" of AcrH. AopB adopts a novel fold, and its transmembrane regions form two pairs of helical hairpins. From these structural studies and associated cellular assays, we deduced the topology of the assembled T3SS translocon; both termini remain extracellular after membrane insertion.

Original languageEnglish
Pages (from-to)2022-2031
Number of pages10
JournalStructure
Volume23
Issue number11
DOIs
StatePublished - 3 Nov 2015

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