Sialyltransferase Family

All members of the sialyltransferase family share a highly conserved so called sialyl motif (designated L for large) in their primary amino acid sequence this motif has been formd to participate in the binding of the common donor substrate CMP-NeuAc [120], In addition to this sialyl motif L a smaller more C-terminally located 

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Kojima N, Yoshida Y, Kurosawa N, Lee YC, Tsuji S. Enzymatic activity of a developmen-tally regulated member of the sialyltransferase family (STX) evidence for a2,8-sialyltrans-ferase activity toward N-linked oligosaccharides. FEBS Lett. 1.995 360 1-4. 

In addition to the variations of the GT-A and GT-B fold described above for sialyltransferases (7, 8) and fucosyltrans-ferases (17), a distinct GT-C fold family has been predicted for GTs that use lipid linked donors. The crystal structures of the GT domain of the peptidoglycan glycosyltransferase from Staphylococcus aureus (18) (Fig. 3f) and Aquifex aeolicus, (26) show structural similarity to the bacteriophage k-lysozyme. These novel structures demonstrate the possibility of additional folds. 

Livingston BD, Paulson JC (1993) Polymerase chain reaction cloning of a developmentally regulated member of the sialyltransferase gene family. J Biol Chem 268 11504-11507... 

The first structure determined for a sialyltransferase (Cstll from Campylobacter jejuni of family GT42 see O Fig. 8c) revealed an unusual variant of the GT-A fold [350]. The protein displays a similar t) e of fold as the canonical GT-A fold, but with some differences in the connectivity of /3-strands (parallel /3-sheet of topology 8712456) and it has no DxD motif. Therefore the Cstll structure represents a new type of fold. Another prokaryotic sialyltransferase has, though, a GT-B fold (see O Table 2). 

Kitagawa H, Livingston BD, Paulson JC. Cloning of novel genes related to the sialyltransferase gene family. Glycoconj. J. 1993 10 233-234.(Abstract)... 

Wen DX, Livingston BD, Medzihradszky KF, Kelm S, Burlingame AL, et al. Primary Structure of Galbetal,3(4)GlcNAc 2,3-Sialyltransferase Determined by Mass Spectrometry Sequence Analysis and Molecular Cloning—Evidence for a Protein Motif in the Sialyltransferase Gene Family. 7. Biol. Chem. 1992 267 21011 21019. 

There are a number of families of similar sialyltransferases, all related to each other through homology of the sialylmotif which may be the CMP-sialic acid donor substrate binding site [93]. This class of enzymes is discussed further in Chapter 12. Two families of sialyltransferases are known to act on mucin O-glycans, Gal a3-sialyltransferases [94-98] and GalNAc a6-sialyltransferases [99-102]. 

Sialyltransferases (SATs) are a family of glycosyltransferases that transfer sialic acid from the donor substrate CMP-NeuAc to the acceptor-oligosaccharide chains... 

Kitagawa, H., and Paulson, J., 1993b, The sialyltransferase gene family, Glycohiology 3 532. 

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