Identification and functional expression of a second human beta-galactoside alpha2,6-sialyltransferase, ST6Gal II.
BLAST analysis of the human and mouse genome sequence databases using the sequence of the human CMP-sialic acid:beta-galactoside alpha-2,6-sialyltransferase cDNA (hST6Gal I, EC2.4.99.1) as a probe allowed us to identify a putative sialyltransferase gene on chromosome 2. The sequence of the corresponding cDNA was also found as an expressed sequence tag of human brain. This gene contained a 1590 bp open reading frame divided in five exons and the deduced amino-acid sequence didn't correspond to any sialyltransferase already known in other species. Multiple sequence alignment and subsequent phylogenic analysis showed that this new enzyme belonged to the ST6Gal subfamily and shared 48% identity with hST6Gal-I. Consequently, we named this new sialyltransferase ST6Gal II. A construction in pFlag vector transfected in COS-7 cells gave raise to a soluble active form of ST6Gal II. Enzymatic assays indicate that the best acceptor substrate of ST6Gal II was the free disaccharide Galbeta1-4GlcNAc structure whereas ST6Gal I preferred Galbeta1-4GlcNAc-R disaccharide sequence linked to a protein. The alpha2,6-linkage was confirmed by the increase of Sambucus nigra agglutinin-lectin binding to the cell surface of CHO transfected with the cDNA encoding ST6Gal II and by specific sialidases treatment. In addition, the ST6Gal II gene showed a very tissue specific pattern of expression because it was found essentially in brain whereas ST6Gal I gene is ubiquitously expressed.
Krzewinski-Recchi
Marie-Ange
MA
Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS-USTL 8576, Université des Sciences et Technologies de Lille, F-59655 Villeneuve d'Ascq, France. Marie-Ange.Recchi@univ-lille1.fr
Julien
Sylvain
S
Juliant
Sylvie
S
Teintenier-Lelièvre
Mélanie
M
Samyn-Petit
Bénédicte
B
Montiel
Maria-Dolores
MD
Mir
Anne-Marie
AM
Cerutti
Martine
M
Harduin-Lepers
Anne
A
Delannoy
Philippe
P
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002240:Carbohydrate Sequence; D002889:Chromosomes, Human, Pair 2; D018076:DNA, Complementary; D020224:Expressed Sequence Tags; D006801:Humans; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012799:Sialyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
D018076:DNA, Complementary; D012799:Sialyltransferases; C088391:galactosyl-1-3-N-acetylgalactosaminyl-specific 2,6-sialyltransferase