Structural highlights
Publication Abstract from PubMedA large group of bacterial virulence autotransporters including AIDA-I from diffusely adhering E. coli (DAEC) and TibA from enterotoxigenic E. coli (ETEC) require hyper-glycosylation 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). Crystal structure of TibC reveals a characteristic ring-shape dodecamer. The protomer features an N-terminal beta-barrel, a catalytic domain, a beta-hairpin thumb and a unique iron-finger motif. The iron-finger motif contributes to back-to-back dimerization; six dimers form the ring through beta-hairpin thumb-mediated hand-in-hand contact. Structure of ADP-D, D-heptose-bound TibC reveals a sugar transfer mechanism and also the ligand stereoselectivity determinant. Cryo-EM 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. A structural mechanism for bacterial autotransporter glycosylation by a dodecameric heptosyltransferase family.,Yao Q, Lu Q, Wan X, Song F, Xu Y, Hu M, Zamyatina A, Liu X, Huang N, Zhu P, Shao F Elife. 2014 Oct 13;3. doi: 10.7554/eLife.03714. PMID:25310236[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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