6ZLU

Closed-closed state of the Bt1762-Bt1763 levan transport system

Summary for 6ZLU

• Entry DOI: 10.2210/pdb6zlu/pdb
• Related: 6ZLT
• EMDB information: 11273 11274
• Descriptor: SusD homolog, SusC homolog (2 entities in total)
• Functional Keywords: suscd, transporter, levan, tonb-dependent, membrane protein
• Biological source: Bacteroides thetaiotaomicron (strain ATCC 29148 / DSM 2079 / NCTC 10582 / E50 / VPI-5482); More
• Total number of polymer chains: 2
• Total formula weight: 181626.23

Authors

White, J.B.R.,van den Berg, B.,Ranson, N.A. (deposition date: 2020-07-01, release date: 2020-11-11, Last modification date: 2021-01-20)

Primary citation

Gray, D.A.,White, J.B.R.,Oluwole, A.O.,Rath, P.,Glenwright, A.J.,Mazur, A.,Zahn, M.,Basle, A.,Morland, C.,Evans, S.L.,Cartmell, A.,Robinson, C.V.,Hiller, S.,Ranson, N.A.,Bolam, D.N.,van den Berg, B.
Insights into SusCD-mediated glycan import by a prominent gut symbiont.
Nat Commun, 12:44-44, 2021

PubMed 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.

PubMed: 33398001
DOI: 10.1038/s41467-020-20285-y

Experimental method

ELECTRON MICROSCOPY (4.2 Å)