The PTS Galactitol (Gat) Family (TC# 4.A.5) is part of the PTS-AG superfamily. The biochemistry of this family is poorly defined. The only well-characterized member of this family is the galactitol permease of Escherichia coli. However, a homologous IIC protein from Listeria monocytogenes has been shown to be required for D-arabitol fermentation. It presumably functions together with IIA<sup>Gat</sup> and IIB<sup>Gat</sup> homologues. IIC<sup>Gat</sup> is distantly related to IIC<sup>Sgc</sup> of E. coli; IIA<sup>Gat</sup> is distantly related to IIA<sup>Sga</sup> and IIA<sup>Sgc</sup>of E. coli as well as IIA<sup>Mtl</sup> and IIA<sup>Fru</sup>. IIB<sup>Gat</sup> is distantly related to IIB<sup>Sga</sup> and IIB<sup>Sgc</sup> of E. coli. Domains in the LicR/CelR family of transcriptional activators show C-terminal domains exhibiting weak sequence similarity to IIB<sup>Gat</sup> and IIA<sup>Gat</sup>.