摘要

A 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.

  • 出版日期2014-10-13
  • 单位北京大学; 德州学院; 中国科学院; 北京生命科学研究所; 生物大分子国家重点实验室