GT-B glycosyltransferases

Lariviere L, Sommer N, Morera S. Structural evidence of a passive base-flipping mechanism for ACT, an unusual GT-B glycosyltransferase. J. Mol. Biol. 2005 352 139-150. 

FucT This apparently contradictory scenario has in fact arisen in many other GT-B glycosyltransferases with the conclusion being that the metal cofactor simply facilitates the departure of the phosphate leaving group from the active site, but is not directly involved in the glycosidic bond cleavage step. 

The GT-B fold family includes most prokaryotic enzymes that produce secondary metabolites, like the antibiotics streptomycin, oleandomycin (Fig. 1) and vancomycin, and important bacterial cell wall precursors. It is also predicted to contain the vitally important 0-GlcNAc transferase that modifies many nuclear and cytoplasmic proteins and influences gene transcription. The first glycosyltransferase structure reported in 1994 was for the GT-B fold enzyme, P-glucosyltransferase (BGT) from bacteriophage T4 (22). This enzyme attaches glucose to modified... 

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. 

Crystal structures of glycosyltransferases with GT-B (or GTB-like) fold... 

Scheme 6.5 In situ production of donor nucleotide sugars followed by transfer onto an acceptor substrate by two (a, b) glycosyltransferases. (a) Shows the reversed GT [105].

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