This family includes proteins such as drosophila saliva [1], MtN3 involved in root nodule development [3] and a protein involved in activation and expression of recombination activation genes (RAGs) [2]. Although the molecular function of these proteins is unknown, they are almost certainly transmembrane proteins. This family contains a region of two transmembrane helices that is found in two copies in most members of the family. This family also contains specific sugar efflux transporters that are essential for the maintenance of animal blood glucose levels, plant nectar production, and plant seed and pollen development. In many organisims it meditaes gluose transport; in Arabidopsis it is necessary for pollen viability; and two of the rice homologues are specifically exploited by bacterial pathogens for virulence by means of direct binding of a bacterial effector to the SWEET promoter [4].

1: saliva, a new Drosophila gene expressed in the embryonic salivary glands with homologues in plants and vertebrates. Artero RD, Terol-Alcayde J, Paricio N, Ring J, Bargues M, Torres A, Perez-Alonso M; Mech Dev 1998;75:159-162. PMID:9739134

2: Molecular cloning and characterization of a novel stromal cell-derived cDNA encoding a protein that facilitates gene activation of recombination activating gene (RAG)-1 in human lymphoid progenitors. Tagoh H, Kishi H, Muraguchi A; Biochem Biophys Res Commun 1996;221:744-749. PMID:8630032

3: Use of a subtractive hybridization approach to identify new Medicago truncatula genes induced during root nodule development. Gamas P, Niebel Fd, Lescure N, Cullimore J; Mol Plant Microbe Interact 1996;9:233-242. PMID:8634476

4: Sugar transporters for intercellular exchange and nutrition of pathogens. Chen LQ, Hou BH, Lalonde S, Takanaga H, Hartung ML, Qu XQ, Guo WJ, Kim JG, Underwood W, Chaudhuri B, Chermak D, Antony G, White FF, Somerville SC, Mudgett MB, Frommer WB; Nature. 2010;468:527-532. PMID:21107422