 A second putative holin gene ("gp5") encoding a protein (Gp5) with a predicted single N-terminal TMS was identified at the end of the Ms6 lytic operon.Neither the putative class II holin nor the single TMS polypeptide could trigger lysis in pairwise combinations with the endolysin LysA in "Escherichia coli".However, further studies have shown that Ms6's Gp4 and Gp5 interact with each other.