Molecular cloning and characterization of a novel human galactose 3-O-sulfotransferase that transfers sulfate to gal beta 1-->3galNAc residue in O-glycans.
We have identified a novel galactose 3-O-sulfotransferase, termed Gal3ST-4, by analysis of an expression sequence tag using the amino acid sequence of human cerebroside 3'-sulfotransferase (Gal3ST-1). The isolated cDNA contains a single open reading frame coding for a protein of 486 amino acids with a type II transmembrane topology. The amino acid sequence of Gal3ST-4 revealed 33%, 39%, and 30% identity to human Gal3ST-1, Gal beta 1-->3/4GlcNAc:-->3'-sulfotransferase (Gal3ST-2) and Gal beta 1-->4GlcNAc:-->3'-sulfotransferase (Gal3ST-3), respectively. The Gal3ST-4 gene comprised at least four exons and was located on human chromosome 7q22. Expression of Gal3ST-4 in COS-7 cells produced a sulfotransferase activity that catalyzes the transfer of [(35)S]sulfate to the C-3' position of Gal beta 1-->3GalNAc alpha 1-O-Bn. Gal3ST-4 recognizes Gal beta 1-->3GalNAc and Gal beta 1-->3(GlcNAc beta 1-->6)GalNAc as good substrates, but not Gal beta 1-->3GalNAc(OH) or Gal beta 1-->3/4GlcNAc. Asialofetuin is also a good substrate, and the sulfation was found exclusively in O-linked glycans that consist of the Gal beta 1-->3GalNAc moiety, suggesting that the enzyme is specific for O-linked glycans. Northern blot analysis revealed that 2.5-kilobase mRNA for the enzyme is expressed extensively in various tissues. These results suggest that Gal3ST-4 is the fourth member of a Gal:-->3-sulfotransferase family and that the four members, Gal3ST-1, Gal3ST-2, Gal3ST-3, and Gal3ST-4, are responsible for sulfation of different acceptor substrates.
Seko
A
A
Department of Biochemistry, Sasaki Institute, 2-2, Kanda-Surugadai, 2-3, Chiyoda-ku, Tokyo 101-0062, Japan.
Hara-Kuge
S
S
Yamashita
K
K
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D006801:Humans; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000378:metabolism; D016415:Sequence Alignment; D013379:Substrate Specificity; D013431:Sulfates / Q000378:metabolism; D015238:Sulfotransferases / Q000235:genetics* / Q000378:metabolism
D011134:Polysaccharides; D013431:Sulfates; D015238:Sulfotransferases; C097036:galactose 3-O-sulfotransferase