This family includes the periplasmic binding proteins, and the LacI family transcriptional regulators. The periplasmic binding proteins are the primary receptors for chemotaxis and transport of many sugar based solutes. The LacI family of proteins consist of transcriptional regulators related to the lac repressor. In this case, generally the sugar binding domain binds a sugar which changes the DNA binding activity of the repressor domain (Pfam:PF00356).

1: 1.7 A X-ray structure of the periplasmic ribose receptor from Escherichia coli. Mowbray SL, Cole LB; J Mol Biol 1992;225:155-175. PMID:1583688

2: Crystal structure of the lactose operon repressor and its complexes with DNA and inducer. Lewis M, Chang G, Horton NC, Kercher MA, Pace HC, Schumacher MA, Brennan RG, Lu P; Science 1996;271:1247-1254. PMID:8638105