1.E.72.  The Archaeal/Bacterial 4 TMS Putative Holin (AB4Holin) Family  

The AB-4Holin family includes many small proteins, all of which have 4 TMSs per polypeptide chain.  Homology with SMR-like proteins has been considered but not established, while sequence similarities with holins in Holin III Superfamily are considerable.  Additional bacterial homologues may be found in other TC Families containing 4 TMS members.  Other homologs may have 3 TMSs because these sequences are not complete.  TC family 9.B.106 members have 3 or 4 TMSs with C-terminal hydrophylic domains, and the N-terminal TMSs may be homologous to those of members of Holin family 1.E.72.