ST3Gal-IV is a CMP-N-acetylneuraminate: β-galacotside α2-3-sialyltransferase (Galβ1-4(3)GlcNAc α2-3-sialyltransferase) (Tsuji et al. 1996). Expression cloning with cytotoxic lectin resistance selection has successfully isolated a cDNA encoding human ST3Gal-IV. ST3Gal-IV is a type II membrane protein, as are most other glycosyl- transferases. It has three conserved motifs, sialylmotif L, S, and VS, within the active domain. ST3Gal-IV also has a Kurosawa motif, as seen in the ST3Gal family and two members of the ST6GalNAc family (Tsuji 1999). ST3Gal-IV mainly catalyzes the α2- 3-sialylation of type II (Galβ1-4GlcNAc) sequence in N-linked glycan chains. Subsequent α1-3-fucosylation to the GlcNAc residue results in the formation of sialyl Lewis X, which is recognized by the selectin family, cell adhesion molecules. ST3Gal-IV also catalyzes the α2-3-sialylation of a type I (Galβ1-3GlcNAc) sequence in N-linked glycan chains. In contrast, ST3Gal-III prefers a type I sequence to a type II sequence. Both enzymes rarely utilize a glycolipid such as paragloboside (Galβ1-4GlcNAcβ1-3Galβ1- 4Glc-Cer).
KeywordsExpression Cloning Acceptor Substrate GlcNAc Residue Namalwa Cell Ricinus Communis Agglutinin
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- Tsuji S (1999) Molecular cloning and characterization of sialyltransferases. In: Inoue Y, Lee YC, Troy FA (eds) Sialobiology and other novel forms of glycosylation. Gakushin, Osaka, pp 145–154Google Scholar