Structural relatedness of lysis proteins from colicinogenic plasmids and icosahedral coliphages

The host-lysis-inducing functions of phi X174 protein E and MS2 protein Lwere recently shown to reside on the N-terminal and C-terminal halves ofthe two respective lysis proteins. In the present study it is shown thatthe small lysis proteins encoded in various colicinogenic plasmids sharelocal sequence similarities and certain structural characteristics with theessential peptides of their coliphage-coded counterparts. Despite theirdissimilar sizes and origins, it is suggested that the colicinogenic lysisproteins are functionally analogous and evolutionarily related to those oficosahedral single- stranded DNA and RNA phages.