EMD-11277
Open-closed state of the Bt1762-Bt1763 levan transport system
EMD-11277
Single-particle4.7 Å
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Map released: 11/11/2020
Last modified: 06/11/2024
Sample Organism:
Bacteroides thetaiotaomicron (strain ATCC 29148 / DSM 2079 / NCTC 10582 / E50 / VPI-5482)
Sample: Dimeric Bt1762-Bt1763 levan transporter complex
Fitted models: 6zm1 (Avg. Q-score: 0.242)
Deposition Authors: White JBR
,
van den Berg B
Sample: Dimeric Bt1762-Bt1763 levan transporter complex
Fitted models: 6zm1 (Avg. Q-score: 0.242)
Deposition Authors: White JBR
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Insights into SusCD-mediated glycan import by a prominent gut symbiont.
Gray DA,
White JBR
,
Oluwole AO
,
Rath P,
Glenwright AJ
,
Mazur A,
Zahn M
,
Basle A
,
Morland C,
Evans SL
,
Cartmell A
,
Robinson CV
,
Hiller S
,
Ranson NA
,
Bolam DN
,
van den Berg B
(2021) Nat Commun , 12 , 44 - 44
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(2021) Nat Commun , 12 , 44 - 44
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.
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.