38FHSummary for 38FH
| Entry DOI | 10.2210/pdb38fh/pdb |
| EMDB information | 78773 |
| Descriptor | TonB-dependent receptor SusC, Starch-binding protein SusD, MANGANESE (II) ION, ... (4 entities in total) |
| Functional Keywords | tbdt, starch, transport, beta-barrel, suscd, sus, pul, membrane protein |
| Biological source | Bacteroides thetaiotaomicron VPI-5482 More |
| Total number of polymer chains | 2 |
| Total formula weight | 161030.01 |
| Authors | |
| Primary citation | Cadigan, M.C.,Fuentes, N.R.,Salmen, W.,Roberts, J.R.,Ruotolo, B.,Ohi, M.D.,Koropatkin, N.M. Structural analyses of a heterodimeric SusCD complex captures intermediate states of maltooligosaccharide transport. J.Biol.Chem., :113672-113672, 2026 Cited by PubMed Abstract: Bacteroides are abundant gut bacteria with diverse polysaccharide metabolizing capabilities encoded by co-transcribed polysaccharide utilization loci (PULs). The starch utilization system (Sus) is required for starch and α-glucan metabolism in Bacteroides thetaiotaomicron and has served as a model for PUL studies. However, the mechanism of maltooligosaccharide (MOS) transport and the architecture of the SusCD complex remain incompletely understood. Here, we used cryo-electron microscopy to capture multiple transport-relevant conformations of the SusD lipoprotein and the TonB-dependent transporter SusC in both unliganded and ligand-bound states. In the absence of ligand, SusCD adopts three conformations including an open state in which SusD is displaced from SusC, a state containing the SusC plug, and a state lacking density for the SusC plug. Three-dimensional variability analysis of the structure where SusD is displaced from SusC reveals continuous SusD mobility coupled to movement of the SusC N-terminus. The maltoheptaose-bound SusCD structure reveals two binding sites, one at the SusD-SusC interface and a second within SusC, indicating how MOS stabilizes a closed SusCD assembly. Notably, all structures show that SusCD is a heterodimer, unlike other Sus-like transporters that assemble into SusCD heterotetramers. Native mass spectrometry confirms this heterodimeric stoichiometry, and comparisons with other SusCD-like complexes suggest a structural basis for this distinct assembly of SusCD. Together, these data define substrate binding and intermediate transport states in a canonical PUL system and reveal architectural divergence among Sus-like carbohydrate transport complexes in Bacteroides. PubMed: 42914029DOI: 10.1016/j.jbc.2026.113672 PDB entries with the same primary citation |
| Experimental method | ELECTRON MICROSCOPY (3.1 Å) |
Structure validation
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