the "mycobacterial" 2 tms phage holin (m2 hol) family (tc# 1.e.36) is a group of transporters belonging to the holin superfamily vii. the "mycobactrerial" 2 transmembrane segment (tms) holins have been identified and recognized by catalao et al (2012). the "mycobacterium" phage d29 gp11 protein (tc# 1.e.36.1.7) is a holin that, upon expression, rapidly kills both "e. coli" and "mycobacterium smegmatis". shortening gp11 from its c-terminus resulted in diminished cytotoxicity and smaller holes. the two tmss at the n-terminus alone do not integrate into the cytoplasmic membrane and do not show toxicity. fusion of the two tmss and a small c-terminal coiled-coil region resulted in restoration of cell killing. the second tms is dispensable for toxicity. the gp11 c-terminal region is therefore necessary but not sufficient for toxicity.