24GD
Crystal structure of apo HpsK from Ruegeria pomeroyi, Crystal form 2
Summary for 24GD
| Entry DOI | 10.2210/pdb24gd/pdb |
| Descriptor | Dihydroxypropanesulfonate (DHPS) TRAP transporter, SULFATE ION (3 entities in total) |
| Functional Keywords | solute binding protein, trap transporter, protein binding |
| Biological source | Ruegeria pomeroyi DSS-3 |
| Total number of polymer chains | 2 |
| Total formula weight | 73306.31 |
| Authors | |
| Primary citation | Barber, H.,Borusak, S.,Stewart, A.W.E.,Tahir, H.,Scott, N.E.,Schleheck, D.,Lee, M.,Williams, S.J. Chiral recognition of 2,3-dihydroxypropanesulfonate by bacterial transport proteins adapted to distinct ecological niches. Chem Sci, 2026 Cited by PubMed Abstract: Bacterial catabolism of 2,3-dihydroxypropanesulfonate (DHPS) links algal production to marine degradation and connects sulfosugar metabolism to sulfide production in the gut. In surface seawater, DHPS occurs as a dilute, mixed / pool, whereas in the anaerobic gut it is produced predominantly as -DHPS through bacterial sulfoglycolysis pathways. Uptake is achieved tripartite ATP-independent periplasmic (TRAP) transporters that employ periplasmic substrate-binding proteins (HpsK), but the molecular basis of enantiomer recognition has not been defined. Here, we compare HpsK proteins from the marine bacterium and the gut anaerobe using proteomics, biophysical analysis, X-ray crystallography, and bioinformatics. HpsK binds both - and -DHPS with low-nanomolar affinity ( 5-9 nM), whereas HpsK binds selectively to -DHPS ( 530 nM), representing an ∼100-fold difference in affinity and strict stereoselectivity. Crystal structures reveal two contrasting strategies for chiral recognition: HpsK accommodates both enantiomers through subtle side-chain "toggling" within an otherwise conserved binding pocket, whereas HpsK achieves stereoselectivity through a distinct hydrogen-bonding network and a binding site that sterically excludes -DHPS. Sequence similarity and genome neighbourhood analyses place these proteins in separate clusters associated with oxidative (HpsNOP) or glycyl radical enzyme-linked (HpsGH/HpfGH) pathways. These findings show how changes in binding-site architecture tune ligand stereoselectivity and illustrate the adaptation of TRAP-associated substrate binding proteins to distinct ecological and metabolic niches. PubMed: 42441157DOI: 10.1039/d6sc02372j PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (1.897 Å) |
Structure validation
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