PROSITE documentation PDOC00680
Sodium:galactoside symporter family signature


It has been shown [1] that integral membrane proteins that mediate the intake of a wide variety of molecules with the concomitant uptake of sodium ions (sodium symporters) can be grouped, on the basis of sequence and functional similarities into a number of distinct families. One of these families is known as the sodium:galactoside symporter family (SGF) and currently consists of the following proteins:

  • The melibiose carrier (gene melB) from a variety of enterobacteria. This protein is responsible for melibiose transport and is capable of using hydrogen, sodium, and lithium cations as coupling cations for cotransport.
  • The lactose permease from Lactobacillus (gene lacS or lacY). This protein is responsible for the transport of β-galactosides into the cell, with the concomitant export of a proton. It consists of two domains; a N- terminal SGF domain and a C-terminal domain that resembles that of enzyme IIA of the PEP:sugar phosphotransferase system.
  • The raffinose permease from Pediococcus pentosaceus. It also consists of a N-terminal SGF domain and a C-terminal IIA domain.
  • The glucuronide carrier (gene gusB or uidP) from Escherichia coli.
  • The xylose transporter (gene xylP) from Lactobacillus pentosus.
  • Escherichia coli hypothetical protein yagG.
  • Escherichia coli hypothetical protein yicJ.
  • Escherichia coli hypothetical protein yihO.
  • Escherichia coli hypothetical protein yihP.
  • Bacillus subtilis hypothetical protein yjmB.
  • Bacillus subtilis hypothetical protein ynaJ.

Like sugar transport proteins, these integral membrane proteins are predicted to comprise twelve membrane spanning domains. As a signature pattern we selected a highly conserved region which is located in a cytoplasmic loop between the second and third transmembrane regions. This region starts with a conserved aspartate which has been shown [2], in melB, to be important for the activity of the protein.

Last update:

December 2004 / Pattern and text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

NA_GALACTOSIDE_SYMP, PS00872; Sodium:galactoside symporter family signature  (PATTERN)


1AuthorsReizer J. Reizer A. Saier M.H. Jr.
TitleA functional superfamily of sodium/solute symporters.
SourceBiochim. Biophys. Acta 1197:133-166(1994).
PubMed ID8031825

2AuthorsPourcher T. Deckert M. Bassilana M. Leblanc G.
TitleMelibiose permease of Escherichia coli: mutation of aspartic acid 55 in putative helix II abolishes activation of sugar binding by Na+ ions.
SourceBiochem. Biophys. Res. Commun. 178:1176-1181(1991).
PubMed ID1872836

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