9.B.18 The Xanthan Glycosyl Transferase, GumD (GumD) Family
The GumD family cosists of a large number of glycosyltransferases involved in exo-polysaccharide biosynthesis and export. GumD of Xanthomonas campestris is a costituent of a multicomponent system involved in the biosynthesis and export to the cell surface. Some of the constituents of this system include GumB (TC# 1.B.18.3.7) and GumC (TC#8.A.3.1.3) (Bianco et al. 2014). The N-terminus of GumD (residues 30 - 140) consists of a domain of closely packed 4 TMSs, followed by a hydrophilic domain that includes 1 or 2 additional TMSs. Residues 75 - 275 consist of the NADB_Rossmann or CoA binding_3 domain, while residues 300 to the end consist of the Bacterial Transferase (bac_transf) domain of CDD.
The glycosyl transferase, GumD, of 484 aas and 5 or 6 TMSs, involved in xanthan gum polysaccharide synthesis and export (Bianco et al. 2014). The N-terminus consists of a closely packed 4 TMS domain (residues 30 - 140), followed by a hydrophilic domain that includes 1 or 2 additional TMSs. Residues 75 - 275 consist of the NADB_Rossmann or CoA binding_3 domain, while residues 300 to the end consist of the Bacterial Transferase (bac_transf) domain of CDD.
GumD of Xanthomonas campestris
Exopolysaccharide biosynthesis polyprenyl glycosylphosphotransferase of 518 aas and 6 TMSs, 4 N-terminal and 2 more centrally located in the large hydrophilic domain.
Glycosyltransferase of Microbacterium laevaniformans
Putative UDP-N-acetylgalactosamine-undecaprenyl-phosphate N-acetylgalactosaminephosphotransferase of 453 aas and 7 TMSs.
Putative transferase of Pedobacter glucosidilyticus
UDP-Gal:undecaprenolphosphate Gal-1-P transferase WbaP with 376 aas and 5 TMSs in a 4 + 1 arrangement.
WbaP of E. coli
Polyisoprenyl-phosphate:hexose-1-P transferase, EpsZ (MXAN_7415), of 494 aas and 5 or 6 TMSs in a 4 or 5 TMS (residues 1 - 150 aas) plus 1 TMS at about residue 310. It is responsible for the initiation of repeat unit synthesis and has galactose-1-P transferase activity (Pérez-Burgos et al. 2020). Its gene is adjacent to the polysaccharide flippase, Wzx (TC# 2.A.66.12.12) and the outer membrane exopolysaccharide exporter (TC# 1.B.18.3.9).
EpsZ of Myxococcus xanthus
Putative capsular polysaccharide biosynthetic enzyme, WbpM of 626 aas and 4 N-terminal TMSs.
WbpM of Bdellovibrio bacteriovorus
Polysaccharide biosynthesis protein of 640 aas and 4 N-terminal TMSs.
PS biosynthesis protein of Clostridium algidicarnis
Exopolysaccharide synthesis protein of 626 aas and 5 N-terminal TMSs.
EPS biosynthesis protein of Burkholderia vietnamiensis
dTDP-glucose 4,6-dehydratase 2, RffG, of 355 aas and possibly one N-terminal TMS. It catalyzes the dehydration of dTDP-D-glucose to form dTDP-6-deoxy-D-xylo-4-hexulose via a three-step process involving oxidation, dehydration and reduction (Hegeman et al. 2001). RffG increases the survival rate after exposure of E. coli to acid stress by 4500 times (Yang et al. 2022).
RffG of E. coli