The β-proteobacterial holin (BP-Hol) family (TC# 1.E.50) is a small family that includes members derived from a number of Burkholderia phage as well as a Poloromonas species.
Members of Saier Bioinformatics Lab at University of California, San Diego found that the BP-Hol family is most closely related to the T7 holin family (TC# 1.E.6).
[1] These proteins are of 60 to 110 amino acyl residues (aas) in length and exhibit 1 or 2 transmembrane segments (TMSs).
Some are annotated as type II hollins and may be related to members of the T7 Holin family (TC# 1.E.6), although BP-Hol proteins remain functionally uncharacterized.
A representative list of the proteins belonging to the BP-Hol family can be found in the Transporter Classification Database.