It is one of the seven different holin superfamilies in total.
In general, these proteins are thought to play a role in regulated cell death, although functionality varies between families and individual members.
[1] This family is made up of over 270 putative pore-forming proteins, all from Bacillota.
On average, proteins belonging to the holin I superfamily are about 100 amino acyl residues (aas) in length, although a large size variation exists among proteins of this superfamily.
There does not seem to be deviation from the standard two transmembrane segments that these proteins possess.