2.A.129.  The Lipid-linked Sugar Translocase (LST) Family

Shigella flexneri bacteriophage SfX, SfV and SfII each has a 3-gene operon encoding a glucosyltransferase (GtrX), which is involved in O antigen modification (serotype Y to serotype X). This operon is responsible for full O antigen conversion. Besides the gtrX gene, the other two genes in the gtr locus of SfX are also involved in the O antigen modification process. The first gene in the cluster (gtrA) encodes a small hydrophobic protein involved in the translocation of lipid-linked glucose across the cytoplasmic membrane. The second gene in the cluster (gtrB) encodes an enzyme catalysing the transfer of the glucose residue from UDP-glucose to a lipid carrier. The third gene (gtrX) encodes a bacteriophage-specific glucosyltransferase which is largely responsible for the final step, i.e. attaching the glucosyl molecules onto the correct sugar residue of the O antigen repeat unit. A three-step model for the glucosylation of bacterial O antigen has been proposed (Guan et al. 1999).  Salmonella phage P22 also has genes involved in serotype conversion, and they are homologous to the Shigella phage operons cited above (Vander Byl and Kropinski 2000). E. coli also has these genes, proabably because they were incorporated  into the bacterial chromosome (Adams et al. 2001). The Shigella SfV and SfX phage GtrX proteins have 4 TMSs (Korres et al. 2005). The 12-2 antigen is a S. enterica subspecies I-specific LPS modification enhances long-term intestinal colonization (Bogomolnaya et al. 2008).

The Mycobacterium tuberculosis homologue GtrA (Rv3789) (TC# 2.A.129.1.2) may be an anchor protein recruiting AftA, the first arabinosyl transferase involved in arabinogalactan biosynthesis, rather than a lipid flippase (Kolly et al. 2015).

This family belongs to the Transporter-Opsin-G protein-coupled receptor (TOG) Superfamily.



Adams, M.M., G.E. Allison, and N.K. Verma. (2001). Type IV O antigen modification genes in the genome of Shigella flexneri NCTC 8296. Microbiology 147: 851-860.

Bogomolnaya, L.M., C.A. Santiviago, H.J. Yang, A.J. Baumler, and H.L. Andrews-Polymenis. (2008). ''Form variation'' of the O12 antigen is critical for persistence of Salmonella Typhimurium in the murine intestine. Mol. Microbiol. 70: 1105-1119.

De Lay, N.R. and J.E. Cronan. (2008). Genetic interaction between the Escherichia coli AcpT phosphopantetheinyl transferase and the YejM inner membrane protein. Genetics 178: 1327-1337.

Guan, S., D.A. Bastin, and N.K. Verma. (1999). Functional analysis of the O antigen glucosylation gene cluster of Shigella flexneri bacteriophage SfX. Microbiology 145(Pt5): 1263-1273.

Kolly, G.S., R. Mukherjee, E. Kilacsková, L.A. Abriata, M. Raccaud, J. Blaško, C. Sala, M. Dal Peraro, K. Mikušová, and S.T. Cole. (2015). GtrA Protein Rv3789 Is Required for Arabinosylation of Arabinogalactan in Mycobacterium tuberculosis. J. Bacteriol. 197: 3686-3697.

Korres, H., M. Mavris, R. Morona, P.A. Manning, and N.K. Verma. (2005). Topological analysis of GtrA and GtrB proteins encoded by the serotype-converting cassette of Shigella flexneri. Biochem. Biophys. Res. Commun. 328: 1252-1260.

Vander Byl, C. and A.M. Kropinski. (2000). Sequence of the genome of Salmonella bacteriophage P22. J. Bacteriol. 182: 6472-6481.


TC#NameOrganismal TypeExample

Bactoprenol-linked glucose translocase of 120 aas and 4 TMSs. Involved in O antigen modification by translocating bactoprenol-linked glucose across the cytoplasmic membrane (Guan et al. 1999).

GtrA of Shigella phage SfV (Shigella flexneri bacteriophage V)


GtrA family proteinof 129 aas and 4 TM

UP of Paracoccus aminovorans


GtrA family proteinof 138 aas and 4 TMSs.

GtrA of Lacticigenium naphtae


Arabinogalactan biosynthesis protein of 121 aas and 4 TMSs.  Required for arabinosylation of arabinogalactan, an essential component of the mycobacterial cell wall. May act as an anchor protein recruiting AftA, the first arabinosyl transferase involved in arabinogalactan biosynthesis, rather than a lipid flippase (Kolly et al. 2015).

GtrA of Mycobacterium tuberculosis


Putative lipid-linked sugar transporter of 216 aas and 6 TMSs.

UP of Candidatus Wolfebacteria bacterium


GtrA of 203 aas and 4 TMSs.

GtrA of Corynebacterium kroppenstedtii


Putative flippase GtrA (transmembrane translocase of bactoprenol-linked glucose

GtrA of Nonomuraea pusilla


GtrA family protein of 142 aas and 4 TMSs.

GtrA of Azospirillum oryzae


Lipid-sugar flippase, GtrA, of 128 aas and 4 TMSs.

GtrA of Staphylococcus aureus


Putative flippase GtrA (transmembrane translocase of bactoprenol-linked glucose) of 149 aas and 3 or 4 TMSs.

Putative flippase of Sporobacter termitidis


Uncharacterized protein of 136 aas and 4 TMSs of the GtrA family.

UP of Leuconostoc pseudomesenteroides


TC#NameOrganismal TypeExample

GtrA-like protein of 157 aas and 4 TMSs

GtrA-like protein of Lokiarchaeum sp. GC14_75


GtrA-like protein of 143 aas and 4 putative TMSs.  This protein maybe incomplete, lacking part of its N-terminus.

Uncharacterized protein of Candidatus Heimdallarchaeota


GtrA family protein of 137 aas and 4 TMSs

GtrA of Acidovorax defluvii


GtrA family protein of 190 aas and 4 TMSs

GtrA of Vagococcus fluvialis