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.
Kurosawa
N
N
Department of Glyco Molecular Biology, Institute of Physical and Chemical Research (RIKEN), Saitama, Japan.
Kojima
N
N
Inoue
M
M
Hamamoto
T
T
Tsuji
S
S
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