Molecular cloning and characterization of a dermatan-specific N-acetylgalactosamine 4-O-sulfotransferase

We have identified and characterized an N-acetylgalactosamine-4-O-sulfotran sferase designated dermatan-4-sulfotransferase-1 (D4ST-1) (GenBank (TM) acc ession number AF401222) based on its homology to HNK-1 sulfotransferase. Th e cDNA predicts an open reading frame encoding a type II membrane protein o f 376 amino acids with a 43-amino acid cytoplasmic domain and a 316-amino a cid luminal domain containing two potential N-linked glycosylation sites. D 4ST-1 has significant amino acid identity with HNK-1 sulfotransferase (21.4 %), N-acetylgalactosamine-4-O-sulfotransferase I (GalNAc-4-ST1) (24.7%),N-a cetylgalactosamine-4-O-sulfotransferase 2 (GalNAc-4-ST2) (21.0%), chondroit in-4-O-sulfotransferase 1 (27.3%), and chondroitin-4-O-sulfotransferase 2 ( 22.8%). D4ST-1 transfers sulfate to the C-4 hydroxyl of beta1,4-linked GalN Ac that is substituted with an alpha -linked iduronic acid (IdoUA) at the C -3 hydroxyl. D4ST-1 shows a strong preference in vitro for sulfate transfer to IdoUA alpha1,3GalNAc beta1,4 that is flanked by GlcUA beta1,3GalNAc bet a1,4 as compared with IdoUA alpha1, 3GalNAc beta1,4 flanked by IdoUA alpha1 ,3GalNAc beta1,4. The specificity of D4ST-1 when assayed in vitro suggests that the addition of sulfate to GalNAc occurs immediately after epimerizati on of GlcUA to IdoUA. The open reading frame of D4ST-1 is encoded by a sing le exon located on human chromosome 15q14. Northern blot analysis reveals a single 2.4-kilobase transcript. D4ST-1 message is expressed in virtually a ll tissues at some level but is most highly expressed in pituitary, placent a, uterus, and thyroid. The properties of D4ST-1 indicate that sulfation of the GalNAc moieties in dermatan is mediated by a distinct GalNAc-4-O-sulfo transferase and occurs following epimerization of GlcUA to IdoUA.