A representative list of proteins belonging to the A2-Hol family can be found in the Transporter Classification Database.
The archaeon, Candidatus Nitrosoarchaeum limnia, encodes adjacent genes designated Toxin Secretion/Lysis Holin.
The "toxin" gene encodes a soluble protein of 325 aas stated as belonging to the "Glycosyltransferase GBT-type Superfamily".
The adjacent gene encodes a small protein of 132 aas and 2 TMSs (TC# 9.B.109.1.1) that could be a holin, based on its size and topology.
Paralogues are found in this same organism (Candidatus Nitrosoarchaeum koreensis) and other closely related species.