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glucose/ribose porter family The glucose/ribose porter (GRP) family (TC 2.A.7.5) includes two functionally characterized members, a glucose uptake permease from Staphylococcus xylosus, and a probable ribose uptake permease from Lactobacillus sakei. Both proteins probably function by H(+) symport. This family also includes several putative and hypothetical membrane proteins that are probably involved in sugar transport across bacterial membranes. GRP family proteins have a distinctive topology: 10 putative transmembrane (TM) alpha-helical spanning domains per polypeptide chain, which apparently arose by intragenic duplication of an element encoding a primordial five-TM polypeptide. In Lactococcus lactis, GlcU was identified as the sole non-PTS (phosphoenolpyruvate:phosphotransferase systems) permease involved in the transport of glucose, which is driven by the proton-motive force. A gene from Bacillus subtilis, ycxE, that is homologous to glcU, could substitute for glcU in Escherichia coli glucose growth experiments and restored glucose repression in Staphylococcus xylosus glcU mutants. RbsU is encoded on the rbsUDK gene cluster, which encodes proteins involved in ribose uptake and phosphorylation. RbsR has been annotated as the repressor of the rbsUDK operon, based on its homology with RbsR repressors. The GRP family belongs to the Drug/Metabolite Transporter (DMT) superfamily (TC 2.A.7). |
Jiyao W et al.(2023). "The conserved domain database in 2023.",