A citrate/Na+ symporter, CitS, seems to be common between "Vibrio cholerae", "Salmonella" Typhi, and "Klebsiella pneumoniae" (6). This symporter uses the influx of sodium ions in order to bring citrate into the cell, which is an important substrate to have for metabolic processes such as decarboxylation of oxaloacetate (6). A H+/amino acid symporter BrnQ can be found in "Lactobacillus delbruckii", and "Pseudomonas aeruginosa" has the BraB symporter for substrates such as glutamate as well (6). Solute/ion symporters are very commonly found in bacteria since they are very important. Homeostasis and regulated uptake for metabolic pathways is essential for bacterial survival. GalP is homologous to GLUT-1 found in mammalian cells (12). Both transporters are MFS transporters and possess 29% sequence identity (4). GLUT-1 is a glucose transporter present in most mammalian cells (Figure 5) (12). Its structure is nearly identical to that of GalP – possessing cytoplasmic amino and carboxy termini, twelve membrane spanning α helices, a periplasmic glycosylation site between helices 1 and 2, and a cytoplasmic α-helix loop between helices 6 and 7 (12). GLUT-1 ranges from 45 to 55 kDa; the size variation depends upon the extent of glycosylation (12). While GLUT-1 is found in most mammalian cells, certain tissue types express this transporter more so than others. GLUT-1 is expressed in high levels on erythrocytes, embryonic cells, fibroblasts, and endothelial cells (12). GLUT-1 is also one of the main transporters involved in transporting glucose across the blood brain barrier (12). Generally, GLUT-1 acts as a facilitative transporter of glucose, transporter glucose along its concentration gradient. When glucose binds to GLUT-1, it stimulates a conformational change, allowing glucose to be released on the opposite side of the membrane (4,12). GLUT-1 is a bidirectional transporter and possesses glucose binding sites accessible on both the cytoplasmic and extracellular faces (4,12). On the rare occasion that GLUT-1 transports glucose against its concentration gradient, Glut-1 uses an energy source, typically ATP, to move the glucose.