title: A structural mechanism for bacterial autotransporter glycosylation by a dodecameric heptosyltransferase family.
abstract: A large group of bacterial virulence autotransporters including AIDA-I from diffusely adhering E. coli (DAEC) and TibA from enterotoxigenic E. coli (ETEC) require hyperglycosylation for functioning. Here we demonstrate that TibC from ETEC harbors a heptosyltransferase activity on TibA and AIDA-I, defining a large family of bacterial autotransporter heptosyltransferases (BAHTs). The crystal structure of TibC reveals a characteristic ring-shape dodecamer. The protomer features an N-terminal β-barrel, a catalytic domain, a β-hairpin thumb, and a unique iron-finger motif. The iron-finger motif contributes to back-to-back dimerization; six dimers form the ring through β-hairpin thumb-mediated hand-in-hand contact. The structure of ADP-D-glycero-β-D-manno-heptose (ADP-D,D-heptose)-bound TibC reveals a sugar transfer mechanism and also the ligand stereoselectivity determinant. Electron-cryomicroscopy analyses uncover a TibC-TibA dodecamer/hexamer assembly with two enzyme molecules binding to one TibA substrate. The complex structure also highlights a high efficient hyperglycosylation of six autotransporter substrates simultaneously by the dodecamer enzyme complex.
authors.affiliation: Dr Feng Shao's Laboratory, National Institute of Biological Sciences, Beijing, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Yao
authors.affiliation: Dr Feng Shao's Laboratory, National Institute of Biological Sciences, Beijing, China.
authors.forename: Qiuhe
authors.initials: Q
authors.lastname: Lu
authors.affiliation: Dr Niu Huang's Laboratory, National Institute of Biological Sciences, Beijing, China.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Wan
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Song
authors.affiliation: Dr Feng Shao's Laboratory, National Institute of Biological Sciences, Beijing, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Institute of Analytic Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, China.
authors.forename: Mo
authors.initials: M
authors.lastname: Hu
authors.affiliation: Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Austria.
authors.forename: Alla
authors.initials: A
authors.lastname: Zamyatina
authors.affiliation: Institute of Analytic Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, China.
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Liu
authors.affiliation: Dr Niu Huang's Laboratory, National Institute of Biological Sciences, Beijing, China.
authors.forename: Niu
authors.initials: N
authors.lastname: Huang
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhu
authors.affiliation: Dr Feng Shao's Laboratory, National Institute of Biological Sciences, Beijing, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Shao
mesh_terms: D018830:Adhesins, Escherichia coli / Q000378:metabolism*; D020816:Amino Acid Motifs; D001422:Bacterial Adhesion; D055162:Biocatalysis; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D006031:Glycosylation; D016695:Glycosyltransferases / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006539:Heptoses; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013237:Stereoisomerism
chemical_list: C075559:AIDA-I protein, E coli; D018830:Adhesins, Escherichia coli; D029968:Escherichia coli Proteins; D006539:Heptoses; D008024:Ligands; C557497:TibA protein, E coli; D016695:Glycosyltransferases; C086735:heptosyltransferase
keywords: E. coli; bacterial autotransporters; bacterial pathogenesis; biophysics; cryo-EM; enzyme catalysis; enzyme complex; glycosyltransferase; infectious disease; microbiology; structural biology