InterPro domain: IPR039672

This family includes lactose permease (LacY) and its homologues that are members of the sodium:galactoside symporter (TC 2.A.2) family. LacY is found in Firmicute bacteria such as Streptococcus thermophilus , and is required for transport of beta-galactosides into the cell. Cations are co-transported. LacY contains a PTS EIIA type-1 domain, which may be regulatory. It is an integral membrane protein with many transmembrane regions [ 1 ]. Other homologues in this family include the melibiose carrier protein (MelB) from Escherichia coli , which is required for the transport of melibiose and other galactosides [ 2 ]; glucuronide carrier protein (UidB or GusB), also from from E. coli , which transports glucuronide (but is inactive in some strains) [ 3 ]; and isoprimeverose transporter (XylP) from Lactobacillus pentosus , which transports isoprimeverose [ 4 ].

1. Lactose transport system of Streptococcus thermophilus: a hybrid protein with homology to the melibiose carrier and enzyme III of phosphoenolpyruvate-dependent phosphotransferase systems. J. Bacteriol. 171, 244-53
2. Melibiose permease of Escherichia coli: large scale purification and evidence that H+, Na+, and Li+ sugar symport is catalyzed by a single polypeptide. Biochemistry 34, 4412-20
3. The gusBC genes of Escherichia coli encode a glucuronide transport system. J. Bacteriol. 187, 2377-85
4. Cloning, sequence analysis, and characterization of the genes involved in isoprimeverose metabolism in Lactobacillus pentosus. J. Bacteriol. 180, 2312-20