ORC4

TgORC4 has been identified in Toxoplasma gondii as a phosphorylation substrate of the TgCrk4-TgCyc4 CDK complex, placing it downstream of this kinase during cell cycle regulation (PMID:38600241). Beyond this single phosphoproteomic assignment, no further mechanistic detail—including the functional consequence of this phosphorylation, its substrates, or its molecular role—has been characterized in the available corpus.

1. 2024 Medium

   Whether TgORC4 lies downstream of the TgCrk4-TgCyc4 G2/M kinase was unknown; global phosphoproteomics placed TgORC4 among the substrates modulated by TgCrk4 activity, linking it to cell cycle regulation.

   Evidence Global phosphoproteome analysis (mass spectrometry-based substrate identification) in Toxoplasma gondii

   PMID:38600241

   Open questions at the time

   • No direct in vitro kinase assay or mutagenesis confirming TgCrk4 directly phosphorylates TgORC4
   • Functional consequence of the phosphorylation event is undefined
   • The phosphorylation site(s) and their role in TgORC4 activity are not mapped

• The molecular function of TgORC4, its localization, and the biological outcome of its phosphorylation by the TgCrk4-TgCyc4 complex remain to be established.
• No characterization of TgORC4's intrinsic function in the available corpus
• No structural or localization data
• No demonstrated phenotype tied to loss or altered phosphorylation of TgORC4