Acidic protein Thionins are small plant proteins which are toxic to animal cells. They seem to exert their toxic effect at the level of the cell membrane. Their precise function is not known. Leaf-specific thionin THI1.5 137 THN5_HORVU MATNKSIKSVVICVLILGLVLEQVQVEAKSCCKNTTGRNCYNACRFAGGSRPVCATACGCKIISGPTCPRDYPKLNLLPESGEPNATEYCTIGCRTSVCDNMDNVSRGQEMKFDMGLCSNACARFCNDGEVIQSVEA