Crystal structure of TDP-fucosamine acetyltransferase (WecD) from Escherichia coli, an enzyme required for enterobacterial common antigen synthesis

J Bacteriol. 2006 Aug;188(15):5606-17. doi: 10.1128/JB.00306-06.


Enterobacterial common antigen (ECA) is a polysaccharide found on the outer membrane of virtually all gram-negative enteric bacteria and consists of three sugars, N-acetyl-d-glucosamine, N-acetyl-d-mannosaminuronic acid, and 4-acetamido-4,6-dideoxy-d-galactose, organized into trisaccharide repeating units having the sequence -->3)-alpha-d-Fuc4NAc-(1-->4)-beta-d-ManNAcA-(1-->4)-alpha-d-GlcNAc-(1-->. While the precise function of ECA is unknown, it has been linked to the resistance of Shiga-toxin-producing Escherichia coli (STEC) O157:H7 to organic acids and the resistance of Salmonella enterica to bile salts. The final step in the synthesis of 4-acetamido-4,6-dideoxy-d-galactose, the acetyl-coenzyme A (CoA)-dependent acetylation of the 4-amino group, is carried out by TDP-fucosamine acetyltransferase (WecD). We have determined the crystal structure of WecD in apo form at a 1.95-Angstrom resolution and bound to acetyl-CoA at a 1.66-Angstrom resolution. WecD is a dimeric enzyme, with each monomer adopting the GNAT N-acetyltransferase fold, common to a number of enzymes involved in acetylation of histones, aminoglycoside antibiotics, serotonin, and sugars. The crystal structure of WecD, however, represents the first structure of a GNAT family member that acts on nucleotide sugars. Based on this cocrystal structure, we have used flexible docking to generate a WecD-bound model of the acetyl-CoA-TDP-fucosamine tetrahedral intermediate, representing the structure during acetyl transfer. Our structural data show that WecD does not possess a residue that directly functions as a catalytic base, although Tyr208 is well positioned to function as a general acid by protonating the thiolate anion of coenzyme A.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acetyl Coenzyme A / metabolism
  • Amino Acid Sequence
  • Antigens, Bacterial / biosynthesis
  • Binding Sites
  • Dimerization
  • Escherichia coli / enzymology*
  • Escherichia coli / immunology*
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism
  • Fucosyltransferases / chemistry*
  • Fucosyltransferases / genetics
  • Fucosyltransferases / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Sequence Alignment


  • Antigens, Bacterial
  • Escherichia coli Proteins
  • enterobacterial common antigen
  • Acetyl Coenzyme A
  • Fucosyltransferases

Associated data

  • PDB/2FS5
  • PDB/2FT0