Update pycsar.md according to Hackaton guidelines, see...

Update pycsar.md according to Hackaton guidelines, see #227 (closed).

content/3.defense-systems/pycsar.md

@@ -10,11 +10,28 @@ tableColumns:
     Activator: Signaling molecules
     Effector: Membrane disrupting, Nucleotides modifying
     PFAM: PF00004, PF00027, PF00211, PF00899, PF01734, PF10137, PF14461, PF14464, PF18145, PF18153, PF18303, PF18967
+contributors: 
+  - Lucas Paoli
+  - Florian Tesson
 relevantAbstracts:
-    - doi: 10.1016/j.cell.2021.09.031
+  - doi: 10.1016/j.cell.2021.09.031
+  - doi: 10.1038/s41586-022-04716-y
 ---
 
 # Pycsar
+
+## Description
+
+The **py**rimidine **c**yclase **s**ystem for **a**ntiphage **r**esistance (Pycsar) :ref{doi=10.1016/j.cell.2021.09.031} is composed of at least two proteins: a cyclase and diverse effectors. The Pycsar defense system is related to the [CBASS](/defense-systems/cbass) but differs in the signaling molecule produced by the cyclase.
+
+In turn, phages encode anti-Pycsar (Apyc) proteins encoded that counteract Pycsar defenses :ref{doi=10.1038/s41586-022-04716-y}.
+
+## Molecular mechanisms
+
+Pycsar uses cyclic nucleotide (pyrimidine cyclase, cCMP and cUMP) signals to induce cell death via diverse effectors activation and prevent viral propagation.
+
+While Apyc degrades cyclic nucleotide signals to prevent host immune responses :ref{doi=10.1016/j.cell.2021.09.031,10.1038/s41586-022-04716-y}. 
+
 ## Example of genomic structure
 
 The Pycsar is composed of at least 2 proteins: a Cyclase and Effector.
@@ -40,6 +57,19 @@ Proportion of genome encoding the Pycsar system for the 14 phyla with more than
 
 
 ## Structure
+
+### Experimentaly determined structure
+From :ref{doi=10.1016/j.cell.2021.09.031} in *Burkholderia cepacia* LK29:
+
+::molstar-pdbe-plugin
+---
+height: 700
+dataUrls: 
+    - /pycsar/7r65-assembly1_Cyclase_2mer.cif
+---
+::
+
+
 ### Pycsar
 ##### Example 1
 
@@ -99,4 +129,3 @@ end
     style Title3 fill:none,stroke:none,stroke-width:none
     style Title4 fill:none,stroke:none,stroke-width:none
 </mermaid>
-