Galβ1-4GlcNAc α2-6-sialyltransferase (EC 220.127.116.11) catalyzes the incorporation of sialic acids at the terminal positions of glycoconjugates with NeuAc α2-6-Gal linkage. cDNA sequences from mouse, rat, human, and chicken, along with the human genomic DNA sequence and-tissue specific alternative splicing in rat have been described. Also, the domains responsible for localization to the Golgi apparatus and the acceptor substrate specificity, with synthetic acceptors, have been reported. Cloned sialyltrans- ferases have been expressed in cultured eukaryotic cells and in E. coli. Like other sialyltransferases, ST6Gal-I exhibits type II membrane protein topology and has characteristic motifs for sialyltransferases called sialylmotifs L, S, and VS. ST3Gal-II also has a Kurosawa motif (Cys-Xaa75-82-Cys-Xaa-Cys-Ala-Xaa-Vα1-Xaa150–160-Cys; Xaa denotes any amino acid residue) as seen in the ST3Gal family and two members of the ST6GalNAc family (Kurosawa et al. 1996; Tsuji 1999). Currently, ST6Gal-I is the sole member of the ST6Gal subfamily that can also synthesize the ganglioside terminal NeuAc α2-6-Gal glycoconjugates.
KeywordsSialic Acid Acceptor Substrate Bovine Colostrum Membrane Protein Topology Synthetic Acceptor
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