4.A.5 The PTS Galactitol (Gat) Family
The only well-characterized member of the Gat famly is the galactitol permease of E. coli (Noblemann and Lengeler, 1995). However, a homologous IIC protein (38% identity) from Listeria monocytogenes has been shown to be required for D-arabitol fermentation (Saklani-Jusforgues et al., 2001). It presumably functions together with IIAGat and IIBGat homologues. IICGat is distantly related to IICSgc of E. coli (Reizer et al., 1996); IIAGat is distantly related to IIASga and IIASgc of E. coli as well as IIAMtl and IIAFru. IIBGat is distantly related to IIBSga and IIBSgc of E. coli. Domains in the LicR/CelR family of transcriptional activators show C-terminal domains exhibiting weak sequence similiarity to IIBGat and IIAGat (Tchieu et al., 2001). The biochemistry of this family is poorly defined.