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Updated: Sep 11, 2025
08:53
Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092
Published on: October 2, 2017
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Structural and molecular basis for phosphate recognition by SAR11 bacteria
Wen-Jing Zhu1, Chen Wang1,2, Li Liu2
1MOE Key Laboratory of Evolution and Marine Biodiversity, Frontiers Science Center for Deep Ocean Multispheres and Earth System and College of Marine Life Sciences, Ocean University of China, Qingdao, China.
Mbio
|August 13, 2025
Summary
SAR11 bacteria, crucial marine microbes, efficiently acquire phosphate using a unique ATP-binding cassette transporter, CpPstS. This protein
Area of Science:
- Marine microbiology
- Biochemistry
- Structural biology
Background:
- Phosphorus is a key limiting nutrient for marine microorganisms.
- SAR11 bacteria dominate nutrient-limited marine environments due to efficient nutrient transporters.
- Molecular mechanisms of phosphate transport in SAR11 remain unclear.
Purpose of the Study:
- Investigate the phosphate transport system in SAR11 bacterium *Candidatus* Pelagibacter sp. HTCC7211.
- Characterize the substrate-binding protein CpPstS structurally and functionally.
- Elucidate the molecular basis of phosphate recognition in SAR11.
Main Methods:
- Heterologous expression and purification of CpPstS.
- X-ray crystallography to determine the structure of CpPstS-phosphate complex.
- Microscale thermophoresis for binding affinity measurements.
- Phylogenetic and bioinformatic analyses.
Main Results:
- CpPstS binds phosphate with high affinity (Kd = 112 nM).
- Structural analysis reveals a unique binding site and hydrogen-bonding network for phosphate.
- CpPstS possesses an expanded binding cavity, suggesting potential for organic phosphorus binding.
- CpPstS-type proteins are widespread in SAR11 bacteria.
Conclusions:
- The study elucidates the molecular mechanism of high-affinity phosphate transport in SAR11 bacteria.
- Unique structural features of CpPstS explain adaptation to low-phosphorus environments.
- Findings suggest SAR11 bacteria may utilize both inorganic and organic phosphorus, impacting marine biogeochemical cycles.
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