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

• Published in: Nature structural & molecular biology Vol. 22; no. 1; pp. 50 - 56
• Main Authors: Hagelueken, Gregor, Clarke, Bradley R, Huang, Hexian, Tuukkanen, Anne, Danciu, Iulia, Svergun, Dmitri I, Hussain, Rohanah, Liu, Huanting, Whitfield, Chris, Naismith, James H
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.01.2015; Nature Publishing Group
• Subjects: 631/326/88; 631/45/221; 631/45/535; Biochemistry; Biological Microscopy; Crystallography; Crystallography, X-Ray; E coli; Escherichia coli - chemistry; Escherichia coli - enzymology; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - metabolism; Life Sciences; Lipopolysaccharides - chemistry; Lipopolysaccharides - metabolism; Mannosyltransferases - chemistry; Mannosyltransferases - metabolism; Membrane Biology; Microbial polysaccharides; O Antigens - chemistry; O Antigens - metabolism; Pathogens; Physiological aspects; Polymers; Protein Conformation; Protein Structure; Saccharides; Scattering, Small Angle; Structure; Austria
• ISSN: 1545-9993; 1545-9985
• DOI: 10.1038/nsmb.2935

Bacterial LPS O-antigen is synthesized with a narrow size range by polymerase WbdA and terminating protein WbdD. An extended coiled-coil domain in WbdD determines the length of the synthesized O-chain, acting as a molecular ruler. 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.