★ Why we care
The TIR domain is shared between Pycsar and human SARM1 (the protein that kills injured axons). Understanding Pycsar → SARM1 selectivity could yield modulators for peripheral neuropathies.
✦ Bactaegion collective mission○ local·0/ 478 206candidate families touched·0therapeutic hypotheses posted·0annotations completed
Canonical sources
Bactaegion does not duplicate any scientific data. Everything comes from public databases.
★ Curated sources
🔍 Search public databases
Protein domains
📚 Reference bibliography
Tal N. et al., Cyclic CMP and cyclic UMP mediate bacterial immunity against phages, Cell 184 (2021). doi:10.1016/j.cell.2021.09.031
Hsueh B.Y. et al., Cyclic-CMP signaling underlies antiphage immunity, Nat. Microbiol. 8 (2023).
★ Princeps publication
Tal et al. (2021). Cyclic CMP and cyclic UMP mediate bacterial immunity against phages. Cell.
1-25 · clear lead · series 2026/2
Pycsar
Pyrimidine Cyclase System for Antiphage Resistance
The system that speaks in mononucleotides, where everyone else spoke in dinucleotides.
Cousin de CBASS : PycC est une pyrimidine cyclase produisant cCMP/cUMP en réponse au phage. Ces seconds messagers activent l'effecteur PycTIR (domaine TIR, NADase). Pycsar a établi cCMP/cUMP comme nouveaux seconds messagers biologiques — voie majeure pour anti-inflammatoires innés.
- Proteins
- 6
- Host
- bactéries
- Discovery
- Tal N., 2021
- Mechanism
- cyclase cCMP/cUMP → effecteur
Also documented in the V1 library see the full entry →
✦ The story
Everyone knew that antiviral signaling revolved around cyclic dinucleotides (cGAMP, c-di-AMP, c-di-GMP). Then in 2021, Tal and Sorek's team discovered that some bacteria used cyclic mononucleotides (cCMP, cUMP) for exactly the same purpose. It was like discovering that a neighboring dialect had existed all along and nobody had ever heard it. The downstream effector is a TIR domain — a domain we knew about in plants (pathogen resistance) and in humans (axons, immunity), but had not anticipated in bacteria.
Discovered 2021
By Tal, Millman, Sorek et al. (Weizmann Institute)
◇ The detail that lands
Pycsar = Pyrimidine Cyclase System for Anti-phage Resistance. The name pays tribute to the Scotsman who invented low-resolution molecular photo-imaging, Sir Robert Edwards Pyc... no, kidding, it is just an acronym. But the word sounds good enough that it has become a meme in the bacterial defense community.
Sources
- Tal N. et al., Cyclic CMP and cyclic UMP mediate bacterial immunity against phages, Cell 184 (2021). doi:10.1016/j.cell.2021.09.031
- Hsueh B.Y. et al., Cyclic-CMP signaling underlies antiphage immunity, Nat. Microbiol. 8 (2023).
Open leads on Pycsar · 1