PTS L-Ascorbate Family

Homologues of SgaT, like other PTS protein homologues, have been identified in a large number of evolutionarily divergent bacteria, but not in archaea or eukaryotes.^[5] Bacteria that encode SgaT homologues include numerous Gram-negative Pseudomonadota, as well as many low and high G+C Gram-positive bacteria. Except for species of Corynebacterium, Streptomyces, and Bacillus, almost all organisms possessing SgaTBA homologues are human/animal pathogens.

Several organisms have two or more SgaT paralogues, including E. coli, which has three. In some of the homologues found in other bacteria, SgaB domains are fused C-terminal to the SgaT domains. For example, this is true of putative transporters in Vibrio cholerae, Pasteurella multocida and Mycoplasma pulmonis. Homologues of SgaB and SgaA, but not SgaT, are also found in transcriptional activator proteins where they function in regulation rather than sugar transport.^[7]

The group translocation reaction catalyzed by SgaTBA is:

L-ascorbate (out) → L-ascorbate-6-phosphate (in)

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