This family consists of several bacterial TolA proteins as well as two eukaryotic proteins of unknown function. Tol proteins are involved in the translocation of group A colicins. Colicins are bacterial protein toxins, which are active against Escherichia coli and other related species (See Pfam:PF01024). TolA is anchored to the cytoplasmic membrane by a single membrane spanning segment near the N-terminus, leaving most of the protein exposed to the periplasm [1].

1: The Tol proteins of Escherichia coli and their involvement in the translocation of group A colicins. Lazzaroni JC, Dubuisson JF, Vianney A; Biochimie 2002;84:391-397. PMID:12423782