1) Bacterial ribonuclease 
Barnase (a portmanteau of `BActerial` `RiboNucleASE`) is a bacterial protein that consists of 110 amino acids and has ribonuclease activity. It is synthesized and secreted by the bacterium Bacillus amyloliquefaciens, but is lethal to the cell when expressed without its inhibitor barstar. The inhibitor binds to and occludes the ribonuclease act...
Bacterial ribonuclease.