A coiled-coil domain acts as a molecular ruler to regulate O-antigen chain length in lipopolysaccharide

Gregor Hageluken, Bradley R. Clarke, Hexian Huang, Anne Tuukkanen, Iulia Danciu, Dmitri I. Svergun, Rohanah Hussain, Huanting Liu, Chris Whitfield, James H. Naismith*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)


Long-chain bacterial polysaccharides have important roles in pathogenicity. In Escherichia coli O9a, a model for ABC transporter-dependent polysaccharide assembly, a large extracellular carbohydrate with a narrow size distribution is polymerized from monosaccharides by a complex of two proteins, WbdA (polymerase) and WbdD (terminating protein). Combining crystallography and small-angle X-ray scattering, we found that the C-terminal domain of WbdD contains an extended coiled-coil that physically separates WbdA from the catalytic domain of WbdD. The effects of insertions and deletions in the coiled-coil region were analyzed in vivo, revealing that polymer size is controlled by varying the length of the coiled-coil domain. Thus, the coiled-coil domain of WbdD functions as a molecular ruler that, along with WbdA:WbdD stoichiometry, controls the chain length of a model bacterial polysaccharide.

Original languageEnglish
Pages (from-to)50-56
Number of pages7
JournalNature Structural and Molecular Biology
Issue number1
Early online date15 Dec 2014
Publication statusPublished - Jan 2015


  • Escherichia-coli O9A
  • Protein secondary structure
  • Circular-dichroism spectra
  • Klebsiella-pneumoniae
  • Polysaccharide export
  • Bifunctional kinase
  • Injectisome needle
  • Flagellar hook
  • Biosynthesis
  • Transporter


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