Crystal structure of the sulfotransferase domain of human heparan sulfate N-deacetylase/N-sulfotransferase 1

Heparan sulfate N-deacetylase/N-sulfotransferase (HSNST) catalyzes the first and obligatory step in the biosynthesis of heparan sulfates and heparin. The crystal structure of the sulfotransferase domain (NST1) of human HSNST-1 has been determined at 2.3-Å resolution in a binary complex with 3'- phosphoadenosine 5'-phosphate (PAP). NST1 is approximately spherical with an open cleft, and consists of a single α/β fold with a central five-stranded parallel β-sheet and a three-stranded anti-parallel β-sheet bearing an interstrand disulfide bond. The structural regions α1, α6, β1, β7, 5'- phosphosulfate binding loop (between β1 and α1), and a random coil (between β8 and α13) constitute the PAP binding site of NST1. The α6 and random coil (between β2 and α2), which form an open cleft near the 5'-phosphate of the PAP molecule, may provide interactions for substrate binding. The conserved residue Lys-614 is in position to form a hydrogen bond with the bridge oxygen of the 5'-phosphate.