Phage_holin_3_6 is a family of small hydrophobic proteins with two or three transmembrane domains of the Hol-X family. Holin proteins are produced by double-stranded DNA bacteriophages that use an endolysin-holin strategy to achieve lysis of their hosts. The endolysins are peptidoglycan-degrading enzymes that are usually accumulated in the cytosol until access to the cell wall substrate is provided by the holin membrane lesion.