Update abib.md

#299 (closed)

content/3.defense-systems/abib.md

@@ -9,12 +9,24 @@ tableColumns:
     Sensor: Unknown
     Activator: Unknown
     Effector: Unknown
+contributors:
+    - Nathalie Bechon
 relevantAbstracts:
     - doi: 10.1023/A:1002027321171
     - doi: 10.1016/j.mib.2005.06.006
+    - doi: 10.1128/aem.57.12.3547-3551.1991
+    - doi: 10.1046/j.1365-2958.1996.371896.x
 ---
 
 # AbiB
+
+## Description
+AbiB is a single-protein abortive infection defense system from *Lactococcus* that degrades mRNA.
+
+## Molecular mechanism
+AbiB system is still poorly understood. It is a single-protein system that was described as an abortive infection system. Upon phage infection, AbiB activation leads to a strong degradation of mRNAs:ref{doi=10.1046/j.1365-2958.1996.371896.x} that is expected to be the mechanism of phage inhibition. AbiB expression is constitutive and does increase during phage infection. It is only activated during phage infection, most likely through the recognition of an early phage protein. Which protein, and whether this activation is direct or indirect remains to be elucidated.
+
+## Example of genomic structure
 The AbiB system is composed of one protein: AbiB.
 
 Here is an example found in the RefSeq database: