HtxB from Pseudomonas stutzeri in complex with phosphite to 1.25 A resolution

Experimental Data Snapshot

  • Resolution: 1.25 Å
  • R-Value Free: 0.170 
  • R-Value Work: 0.145 
  • R-Value Observed: 0.146 

Starting Model: experimental
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Phosphite binding by the HtxB periplasmic binding protein depends on the protonation state of the ligand.

Adams, N.B.P.Robertson, A.J.Hunter, C.N.Hitchcock, A.Bisson, C.

(2019) Sci Rep 9: 10231-10231

  • DOI: https://doi.org/10.1038/s41598-019-46557-2
  • Primary Citation of Related Structures:  
    6EMN, 6GHQ, 6GHT

  • PubMed Abstract: 

    Phosphorus acquisition is critical for life. In low phosphate conditions, some species of bacteria have evolved mechanisms to import reduced phosphorus compounds, such as phosphite and hypophosphite, as alternative phosphorus sources. Uptake is facilitated by high-affinity periplasmic binding proteins (PBPs) that bind cargo in the periplasm and shuttle it to an ATP-binding cassette (ABC)-transporter in the bacterial inner membrane. PtxB and HtxB are the PBPs responsible for binding phosphite and hypophosphite, respectively. They recognize the P-H bond of phosphite/hypophosphite via a conserved P-H...π interaction, which confers nanomolar dissociation constants for their respective ligands. PtxB also has a low-level binding affinity for phosphate and hypophosphite, whilst HtxB can facilitate phosphite uptake in vivo. However, HtxB does not bind phosphate, thus the HtxBCDE transporter has recently been successfully exploited for biocontainment of genetically modified organisms by phosphite-dependent growth. Here we use a combination of X-ray crystallography, NMR and Microscale Thermophoresis to show that phosphite binding to HtxB depends on the protonation state of the ligand, suggesting that pH may effect the efficiency of phosphite uptake by HtxB in biotechnology applications.

  • Organizational Affiliation

    Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Probable phosphite transport system-binding protein HtxB274Stutzerimonas stutzeriMutation(s): 0 
Gene Names: htxB
Find proteins for O69061 (Stutzerimonas stutzeri)
Explore O69061 
Go to UniProtKB:  O69061
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupO69061
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.25 Å
  • R-Value Free: 0.170 
  • R-Value Work: 0.145 
  • R-Value Observed: 0.146 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 40.28α = 90
b = 55.2β = 90
c = 126.33γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XSCALEdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2019-04-17
    Type: Initial release
  • Version 1.1: 2019-07-24
    Changes: Data collection, Database references
  • Version 1.2: 2024-01-17
    Changes: Data collection, Database references, Derived calculations, Refinement description