Update rexab.md

Add description, molecular mechanisms.

link to issue #259

content/3.defense-systems/rexab.md

@@ -10,9 +10,20 @@ tableColumns:
     Activator: Direct
     Effector: Membrane disrupting
     PFAM: PF15968, PF15969
+contributors:
+    - Rachel Lavenir
+relevantAbstracts:
+    - doi: 10.1101/gad.6.3.497
+
 ---
 
 # RexAB
+## Description
+RexB is a transmembrane protein with four transmembrane domains.
+
+## Molecular mechanisms
+As far as we are aware, the molecular mechanism is unknown.
+
 ## Example of genomic structure
 
 The RexAB system is composed of 2 proteins: RexA and, RexB.
@@ -76,13 +87,5 @@ end
     style Title3 fill:none,stroke:none,stroke-width:none
     style Title4 fill:none,stroke:none,stroke-width:none
 </mermaid>
-## Relevant abstracts
 
-::relevant-abstracts
----
-items:
-    - doi: 10.1101/gad.6.3.497
-
----
-::