Substrate specificity and ecological significance of PstS homologs in phosphorus uptake in marine Synechococcus sp. WH8102

Pramita Ranjit, Deepa Varkey, Bhumika S. Shah*, Ian T. Paulsen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)
64 Downloads (Pure)

Abstract

Phosphorus, a vital macronutrient, often limits primary productivity in marine environments. Marine Synechococcus strains, including WH8102, rely on high-affinity phosphate-binding proteins (PstS) to scavenge inorganic phosphate in oligotrophic oceans. However, WH8102 possesses three distinct PstS homologs whose substrate specificity and ecological roles are unclear. The three PstS homologs were heterologously expressed and purified to investigate their substrate specificity and binding kinetics. Our study revealed that all three PstS homologs exhibited a high degree of specificity for phosphate but differed in phosphate binding affinities. Notably, PstS1b displayed nearly 10-fold higher binding affinity (KD = 0.44 µM) compared to PstS1a (KD = 3.3 μM) and PstS2 (KD = 4.3 μM). Structural modeling suggested a single amino acid variation in the binding pocket of PstS1b (threonine instead of serine in PstS1a and PstS2) likely contributed to its higher Pi affinity. Genome context data, together with the protein biophysical data, suggest distinct ecological roles for the three PstS homologs. We propose that PstS1b may be involved in scavenging inorganic phosphorus in oligotrophic conditions and that PstS1a may be involved in transporting recycled phosphate derived from organic phosphate cleavage. The role of PstS2 is less clear, but it may be involved in phosphate uptake when environmental phosphate concentrations are transiently higher. The conservation of three distinct PstS homologs in Synechococcus clade III strains likely reflects distinct adaptations for P acquisition under varying oligotrophic conditions.
Original languageEnglish
Pages (from-to)e0278623
Number of pages15
JournalMicrobiology Spectrum
Volume12
Issue number2
Early online date5 Jan 2024
DOIs
Publication statusPublished - Feb 2024

Bibliographical note

Copyright the Author(s) 2024. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • differential scanning fluorimetry (DSF)
  • high-affinity
  • KEYWORDS phosphate binding protein (PstS)
  • phosphate stress
  • Synechococcus

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