Update 6.defensive-domains.md #332

content/2.general-concepts/6.defensive-domains.md

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 title: Defensive Domains
 layout: article
 toc: true
+contributors:
+    - Hugo Vaysset
 ---
 
-Among proteins involved in defense systems, a few domains appear to be frequent. 
+# What are protein domains ?
+Proteins can typically be decomposed into a set of structural/functional units called "domains" where each individual domain has a specific biological function (e.g. catalyzing a chemical reaction or binding to another protein). The combination of one or several protein domains within a protein determines its biological function. 
+
+# Domain characterization helps to understand the biological function of a protein
+Although a considerable diversity of molecular mechanisms have been described for defense systems, it is striking to observe that some functional domains are recurrently involved in antiphage defense. It is frequent to find the same domain associated with a wide range of distinct domains in different defense systems. It is thought that this modularity of protein domains allows to diversify antiphage defense mechanisms [ ].
+
+To illustrate this idea, we can cite the example of 
+
+# Domain characterization allows to identify evolutionary links between proteins
+
+
+To illustrate this, we can cite :
+-  Toll/Interleukin-1 Receptor (TIR) domains are found in individual components of several antiphage systems like Thoeris (ThsB, PF08937), CBASS, Pycsar.
+
+# References
+[ ] Rousset, F., & Sorek, R. (2023). The evolutionary success of regulated cell death in bacterial immunity. Current opinion in microbiology, 74, 102312.