polypeptide N-acetylgalactosaminyltransferase 18; polypeptide galNAc transferase-like protein 4; galNAc-T-like protein 4; pp-GaNTase-like protein 4; polypeptide N-acetylgalactosaminyltransferase-like protein 4; protein-UDP acetylgalactosaminyltransferase-like protein 4; UDP-galNAc:polypeptide N-acetylgalactosaminyltransferase-like protein 4 (GALNT18 GALNTL4)

Function

• may catalyze initial reaction in O-linked oligosaccharide biosynthesis, transfer of N-acetyl-D-galactosamine residue to Ser or Thr on the nascent glycoprotein

UDP-N-acetyl-D-galactosamine + polypeptide <--> UDP + N-acetyl-D-galactosaminyl-polypeptide

Cofactor: Mn+2, Ca+2

Structure

• belongs to glycosyltransferase 2 family, GalNAc-T subfamily.
• two conserved domains in the glycosyltransferase region:
  • N-terminal domain (domain A, GT1 motif)
    • Mn+2 coordination & substrate binding
  • C-terminal domain (domain B, Gal/GalNAc-T motif)
    • catalytic reaction & UDP-Gal binding
• ricin B-type lectin domain binds to GalNAc & contributes to glycopeptide specificity

Compartment

Golgi membrane

Alternative splicing

named isoforms=2

More general terms

• galactosyltransferase
• glycoprotein

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=374378
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:374378
• UniProt: http://www.uniprot.org/uniprot/Q6P9A2.html