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Phosphite binding by the HtxB periplasmic binding protein depends on the protonation state of the ligand

DOI: 10.1038/s41598-019-46557-2 DOI Help

Authors: Nathan B. P. Adams (The University of Sheffield) , Angus J. Robertson (The University of Sheffield) , C. Neil Hunter (The University of Sheffield) , Andrew Hitchcock (The University of Sheffield) , Claudine Bisson (The University of Sheffield; Birkbeck College, University of London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Scientific Reports , VOL 9

State: Published (Approved)
Published: July 2019
Diamond Proposal Number(s): 12788

Open Access Open Access

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.

Subject Areas: Biology and Bio-materials

Instruments: I03-Macromolecular Crystallography , I04-1-Macromolecular Crystallography (fixed wavelength) , I04-Macromolecular Crystallography


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