Merge branch 'gaps4' into 'main'

gaps4 Added Description & Mechanism in the text

See merge request !41

content/3.defense-systems/gaps4.md

@@ -6,13 +6,23 @@ tableColumns:
       doi: 10.1101/2023.03.28.534373
       abstract: |
         Bacteria are found in ongoing conflicts with rivals and predators, which lead to an evolutionary arms race and the development of innate and adaptive immune systems. Although diverse bacterial immunity mechanisms have been recently identified, many remain unknown, and their dissemination within bacterial populations is poorly understood. Here, we describe a widespread genetic element, defined by the Gamma-Mobile-Trio (GMT) proteins, that serves as a mobile bacterial weapons armory. We show that GMT islands have cargo comprising various combinations of secreted antibacterial toxins, anti-phage defense systems, and secreted anti-eukaryotic toxins. This finding led us to identify four new anti-phage defense systems encoded within GMT islands and reveal their active domains and mechanisms of action. We also find the phage protein that triggers the activation of one of these systems. Thus, we can identify novel toxins and defense systems by investigating proteins of unknown function encoded within GMT islands. Our findings imply that the concept of "defense islands" may be broadened to include other types of bacterial innate immunity mechanisms, such as antibacterial and anti-eukaryotic toxins that appear to stockpile with anti-phage defense systems within GMT weapon islands.
+contributors:
+    - Hugo Vaysset
 relevantAbstracts:
     - doi: 10.1101/2023.03.28.534373
 ---
 
 # GAPS4
 
-## To do 
+## Description
+GAPS4 is a two genes system (GAPS4a and GAPS4b). GAPS stands for GMT-encoded Anti-Phage System. 
+
+GAPS4 is present in both Gram positive and Gram negative 
+GAPS4 activity was assessed in *E. coli* and was shown to be active against T4, P1-vir and lambda-vir and to reduce lysis plaque size of T7 :ref{doi=10.1101/2023.03.28.534373}. 
+
+## Molecular mechanism
+GAPS4a is a nuclease containing a domain from the PDDEXK clan (CL0236) suggesting that the GAPS4 defense system is acting via DNA degradation. Both genes are required for phage defense and were predicted to form a heterodimer. It was shown that the system works causes host DNA degradation upon infection by lambda-vir only, which would suggest that GAPS4 is an abortive infection system :ref{doi=10.1101/2023.03.28.534373}.
+
 
 ## Example of genomic structure
 
@@ -37,6 +47,7 @@ Proportion of genome encoding the GAPS4 system for the 14 phyla with more than 5
 
 
 ## Structure
+
 ### GAPS4
 ##### Example 1