title: Structure of AcrH-AopB Chaperone-Translocator Complex Reveals a Role for Membrane Hairpins in Type III Secretion System Translocon Assembly.
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.
authors.affiliation: Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543 Singapore.
authors.forename: Van Sang
authors.initials: VS
authors.lastname: Nguyen
authors.affiliation: Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543 Singapore.
authors.forename: Chacko
authors.initials: C
authors.lastname: Jobichen
authors.affiliation: Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543 Singapore.
authors.forename: Kang Wei
authors.initials: KW
authors.lastname: Tan
authors.affiliation: Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543 Singapore.
authors.forename: Yih Wan
authors.initials: YW
authors.lastname: Tan
authors.affiliation: Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543 Singapore.
authors.forename: Siew Leong
authors.initials: SL
authors.lastname: Chan
authors.affiliation: Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543 Singapore.
authors.forename: Karthik
authors.initials: K
authors.lastname: Ramesh
authors.affiliation: Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543 Singapore.
authors.forename: Yongming
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543 Singapore.
authors.forename: Yunhan
authors.initials: Y
authors.lastname: Hong
authors.affiliation: X4 Beamline, Brookhaven National Laboratory, Upton, NY, USA.
authors.forename: Jayaraman
authors.initials: J
authors.lastname: Seetharaman
authors.affiliation: Department of Biology, Faculty of Natural and Applied Sciences, Trinity Western University, 7600 Glover Road, Langley, BC V2Y 1Y1, Canada.
authors.forename: Ka Yin
authors.initials: KY
authors.lastname: Leung
authors.affiliation: Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543 Singapore.
authors.forename: J
authors.initials: J
authors.lastname: Sivaraman
authors.affiliation: Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543 Singapore. Electronic address: dbsmokh@nus.edu.sg.
authors.forename: Yu Keung
authors.initials: YK
authors.lastname: Mok
mesh_terms: D016980:Aeromonas hydrophila / Q000737:chemistry; D000595:Amino Acid Sequence; D001665:Binding Sites; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D011485:Protein Binding; D000069296:Type III Secretion Systems / Q000737:chemistry* / Q000378:metabolism
chemical_list: D018832:Molecular Chaperones; D000069296:Type III Secretion Systems