text: The HMG proteins are subdivided into 3 superfamilies each containing a characteristic functional domain:
  * HMGA – contains an AT-hook domain
  ** HMGA1
  ** HMGA2
  * HMGB – contains a HMG-box domain
  ** HMGB1
  ** HMGB2
  ** HMGB3
  ** HMGB4
  * HMGN – contains a nucleosomal binding domain
  ** HMGN1
  ** HMGN2
  ** HMGN3
  ** HMGN4
  ** HMGN5
  Proteins containing any of these embedded in their sequence are known as HMG motif proteins. 
  HMG-box proteins are found in a variety of eukaryotic organisms.
  They were originally isolated from mammalian cells, and named according to their electrophoretic mobility in polyacrylamide gels.