Update gao_iet.md

Add description and no mechanism #221 (closed)

content/3.defense-systems/gao_iet.md

@@ -15,6 +15,17 @@ relevantAbstracts:
 ---
 
 # Gao_Iet
+
+## Description
+
+Gao_Iet or Iet or IetAS was discovered in 2020 among other defense systems by :ref{doi=10.1126/science.aba0372}.
+
+The Iet system is composed of two proteins: IetA (an ATPase) and IetS (a protease) :ref{doi=10.1126/science.aba0372}.
+
+## Molecular mechanism
+
+As far as we are aware, the molecular mechanism is unknown.
+
 ## Example of genomic structure
 
 The Gao_Iet is composed of 2 proteins: IetA and IetS.