The Toxoplasma glucan phosphatase TgLaforin utilizes a distinct functional mechanism that can be exploited by therapeutic inhibitors

Robert D. Murphy, Tiantian Chen, Jianping Lin, Rongjun He, Li Wu, Caden R. Pearson, Savita Sharma, Carl D. Vander Kooi, Anthony P. Sinai, Zhong Yin Zhang, Craig W. Vander Kooi, Matthew S. Gentry

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Toxoplasma gondii is an intracellular parasite that generates amylopectin granules (AGs), a polysaccharide associated with bradyzoites that define chronic T. gondii infection. AGs are postulated to act as an essential energy storage molecule that enable bradyzoite persistence, transmission, and reactivation. Importantly, reactivation can result in the life-threatening symptoms of toxoplasmosis. T. gondii encodes glucan dikinase and glucan phosphatase enzymes that are homologous to the plant and animal enzymes involved in reversible glucan phosphorylation and which are required for efficient polysaccharide degradation and utilization. However, the structural determinants that regulate reversible glucan phosphorylation in T. gondii are unclear. Herein, we define key functional aspects of the T. gondii glucan phosphatase TgLaforin (TGME49_205290). We demonstrate that TgLaforin possesses an atypical split carbohydrate-binding-module domain. AlphaFold2 modeling combined with hydrogen–deuterium exchange mass spectrometry and differential scanning fluorimetry also demonstrate the unique structural dynamics of TgLaforin with regard to glucan binding. Moreover, we show that TgLaforin forms a dual specificity phosphatase domain–mediated dimer. Finally, the distinct properties of the glucan phosphatase catalytic domain were exploited to identify a small molecule inhibitor of TgLaforin catalytic activity. Together, these studies define a distinct mechanism of TgLaforin activity, opening up a new avenue of T. gondii bradyzoite biology as a therapeutic target.

Original languageEnglish
Article number102089
JournalJournal of Biological Chemistry
Issue number7
StatePublished - Jul 2022

Bibliographical note

Publisher Copyright:
© 2022 The Authors


  • AlphaFold2
  • Toxoplasma gondii
  • amylopectin
  • carbohydrate-binding protein
  • differential scanning fluorimetry
  • glucan phosphatase
  • hydrogen exchange mass spectrometry
  • laforin
  • phosphatase
  • size-exclusion chromatography with multiangle light scattering

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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