┬────────────────────────────────────────────────────────────────── Escherichia coli (13-80/86) E2348/69 (18)  
└────────────────────────────────────────────────────────────────┬─── Escherichia coli (25-108/108) B7A (8)  
                                                                 └┬── Escherichia coli MS 196-1 (2)  
                                                                  └─ Escherichia coli (25-108/108) 042 (14)  
  

  
Regulatory protein Cro of bacteriophage BP-933W
 (4)