Cloning and expression of Gal beta 1,3GalNAc-specific GalNAc alpha 2,6-sialyltransferase.
A cDNA clone encoding a new type of GalNAc alpha 2,6-sialyltransferase (ST6GalNAc II) with a structure similar to that of a previously cloned GalNAc alpha 2,6-sialyltransferase (ST6GalNAc I; Kurosawa, N., Hamamoto, T., Lee, Y.-C., Nakaoka, T., Kojima, N., and Tsuji, S. (1994) J. Biol. Chem. 269, 1402-1409) was obtained from chicken testes. The predicted amino acid sequence of ST6GalNAc II encodes a protein with type II transmembrane topology, as found for other glycosyltransferases, and showed 32% identity with that of ST6GalNAc I. Transfection of the full length ST6GalNAc II gene into COS cells led to GalNAc alpha 2,6-sialyltransferase activity with a different substrate specificity from that of ST6GalNAc I. Moreover, asialofetuin after treatment with beta-galactosidase did not serve as an acceptor for this enzyme. 14C-Sialylated oligosaccharides obtained from resialylated asialobovine submaxillary mucin with this enzyme were identical to Gal beta 1,3([14C]NeuAc alpha 2,6)GalNAc-ol but not [14C]NeuAc alpha 2,6GalNAc-ol. These results clearly show that the expressed enzyme is a novel type of sialyltransferase that requires beta-galactoside residues linked to GalNAc residues, whereas sialic acid residues linked to galactose residues are not essential for the activity.
Department of Glyco Molecular Biology, Institute of Physical and Chemical Research (RIKEN), Saitama, Japan.
N
N
Kurosawa
N
N
Kojima
M
M
Inoue
T
T
Hamamoto
S
S
Tsuji
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002240:Carbohydrate Sequence; D002645:Chickens; D003001:Cloning, Molecular; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression; D005796:Genes; D008297:Male; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012799:Sialyltransferases / Q000235:genetics*; D013379:Substrate Specificity; D013737:Testis / Q000201:enzymology
D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D012799:Sialyltransferases; C088391:galactosyl-1-3-N-acetylgalactosaminyl-specific 2,6-sialyltransferase