Crystal structure of an alpha 1,4-N-acetylhexosaminyltransferase (EXTL2), a member of the exostosin gene family involved in heparan sulfate biosynthesis

J Biol Chem. 2003 Apr 18;278(16):14420-8. doi: 10.1074/jbc.M210532200. Epub 2003 Jan 31.


EXTL2, an alpha1,4-N-acetylhexosaminyltransferase, catalyzes the transfer reaction of N-acetylglucosamine and N-acetylgalactosamine from the respective UDP-sugars to the non-reducing end of [glucuronic acid]beta1-3[galactose]beta1-O-naphthalenemethanol, an acceptor substrate analog of the natural common linker of various glycosylaminoglycans. We have solved the x-ray crystal structure of the catalytic domain of mouse EXTL2 in the apo-form and with donor substrates UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine. In addition, a structure of the ternary complex with UDP and the acceptor substrate analog [glucuronic acid]beta1-3[galactose]beta1-O-naphthalenemethanol has been determined. These structures reveal three highly conserved residues, Asn-243, Asp-246, and Arg-293, located at the active site. Mutation of these residues greatly decreases the activity. In the ternary complex, an interaction exists between the beta-phosphate of the UDP leaving group and the acceptor hydroxyl of the substrate that may play a functional role in catalysis. These structures represent the first structures from the exostosin gene family and provide important insight into the mechanisms of alpha1,4-N-acetylhexosaminyl transfer in heparan biosynthesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arginine / chemistry
  • Asparagine / chemistry
  • Aspartic Acid / chemistry
  • Binding Sites
  • COS Cells
  • Catalytic Domain
  • Crystallography, X-Ray
  • Heparitin Sulfate / biosynthesis*
  • Heparitin Sulfate / chemistry
  • Hydrogen Bonding
  • Membrane Proteins*
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • N-Acetylgalactosaminyltransferases / metabolism
  • N-Acetylglucosaminyltransferases / chemistry*
  • Protein Conformation
  • Protein Structure, Tertiary
  • Sequence Homology, Amino Acid
  • Transfection
  • Uridine Diphosphate N-Acetylglucosamine / metabolism


  • Membrane Proteins
  • Aspartic Acid
  • Uridine Diphosphate N-Acetylglucosamine
  • Asparagine
  • Heparitin Sulfate
  • Arginine
  • EXTL2 protein, human
  • N-Acetylgalactosaminyltransferases
  • N-Acetylglucosaminyltransferases
  • UDP-N-acetylgalactosamine (GlcUA-GalNAc-4-sulfate)(4) N-acetylgalactosaminyltransferase

Associated data

  • PDB/1OMX
  • PDB/1OMZ
  • PDB/1ON6
  • PDB/1ON8