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Báo cáo khoa học: Identification and functional expression of a second human b-galactoside a2,6-sialyltransferase, ST6Gal II
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BLASTanalysis of the human and mouse genome sequence databases using the sequence of the human CMP-sialic acid:b-galactoside a-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. | Eur. J. Biochem. 270 950-961 2003 FEBS 2003 doi 10.1046 j.1432-1033.2003.03458.x Identification and functional expression of a second human b-galactoside a2 6-sialyltransferase ST6Gal II Marie-Ange Krzewinski-Recchi1 Sylvain Julien1 Sylvie Juliant2 Melanie Teintenier-Lelievre1 Benedicte Samyn-Petit1 Maria-Dolores Montiel1 Anne-Marie Mir1 Martine Cerutti2 Anne Harduin-Lepers1 and Philippe Delannoy1 1Unite de Glycobiologie Structurale et Fonctionnelle UMR CNRS - USTL 8576 Universite des Sciences et Technologies de Lille F-59655 Villeneuve d Ascq France 2Station de Recherche de Pathologie Comparee UMR CNRS - INRA 5087 F-30380 Saint Christol-lez-Ales France BLAST analysis of the human and mouse genome sequence databases using the sequence of the human CMP-sialic acid b-galactoside a-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 Galb1-4GlcNAc structure whereas ST6Gal I preferred Galb1-4GlcNAc-R disaccharide sequence linked to a protein. The a2 6-linkage was confirmed by the increase of Sambucus nigra agglutininlectin 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 .