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Insights into SusCD-mediated glycan import by a prominent gut symbiont

DOI: 10.1038/s41467-020-20285-y DOI Help

Authors: Declan A. Gray (Newcastle University) , Joshua B. R. White (University of Leeds) , Abraham O. Oluwole (University of Oxford) , Parthasarathi Rath (University of Basel) , Amy J. Glenwright (Newcastle University) , Adam Mazur (University of Basel) , Michael Zahn (University of Basel) , Arnaud Basle (Newcastle University) , Carl Morland (Newcastle University) , Sasha L. Evans (University of Leeds) , Alan Cartmell (University of Liverpool) , Carol V. Robinson (University of Oxford) , Sebastian Hiller (University of Basel) , Neil A. Ranson (University of Leeds) , David N. Bolam (Newcastle University) , Bert Van Den Berg (Newcastle University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Communications , VOL 12

State: Published (Approved)
Published: January 2021
Diamond Proposal Number(s): 13587 , 18598

Open Access Open Access

Abstract: In Bacteroidetes, one of the dominant phyla of the mammalian gut, active uptake of large nutrients across the outer membrane is mediated by SusCD protein complexes via a “pedal bin” transport mechanism. However, many features of SusCD function in glycan uptake remain unclear, including ligand binding, the role of the SusD lid and the size limit for substrate transport. Here we characterise the β2,6 fructo-oligosaccharide (FOS) importing SusCD from Bacteroides thetaiotaomicron (Bt1762-Bt1763) to shed light on SusCD function. Co-crystal structures reveal residues involved in glycan recognition and suggest that the large binding cavity can accommodate several substrate molecules, each up to ~2.5 kDa in size, a finding supported by native mass spectrometry and isothermal titration calorimetry. Mutational studies in vivo provide functional insights into the key structural features of the SusCD apparatus and cryo-EM of the intact dimeric SusCD complex reveals several distinct states of the transporter, directly visualising the dynamics of the pedal bin transport mechanism.

Journal Keywords: Bacteriology; Cryoelectron microscopy; Transporters; X-ray crystallography

Subject Areas: Biology and Bio-materials

Instruments: I03-Macromolecular Crystallography , I04-1-Macromolecular Crystallography (fixed wavelength) , I04-Macromolecular Crystallography