Structural Basis of Ordered Binding of Donor and Acceptor Substrates to the Retaining Glycosyltransferase, Alpha -1,3 GalactosyltransferaseBoix, E., Zhang, Y., Swaminathan, G.J., Brew, K., Acharya, K.R.
(2002) J.Biol.Chem. 277: 28310
- PubMed: 12011052
- DOI: 10.1074/jbc.M202631200
- Primary Citation of Related Structures:  1GWW, 1GX0, 1GX4
- PubMed Abstract:
- Structure of Udp Complex of Udp-Galactose:Beta-Galactoside-Alpha -1,3-Galactosyltransferase at 1.53-A Resolution Reveals a Conformational Change in the Catalytically Important C Terminus
Boix, E.,Swaminathan, G.J.,Zhang, Y.,Natesh, R.,Brew, K.,Acharya, K.R.
(2001) J.Biol.Chem. 276: 48608
Bovine alpha-1,3-galactosyltransferase (alpha3GT) catalyzes the synthesis of the alpha-galactose (alpha-Gal) epitope, the target of natural human antibodies. It represents a family of enzymes, including the histo blood group A and B transferases, tha ...
Bovine alpha-1,3-galactosyltransferase (alpha3GT) catalyzes the synthesis of the alpha-galactose (alpha-Gal) epitope, the target of natural human antibodies. It represents a family of enzymes, including the histo blood group A and B transferases, that catalyze retaining glycosyltransfer reactions of unknown mechanism. An initial study of alpha3GT in a crystal form with limited resolution and considerable disorder suggested the possible formation of a beta-galactosyl-enzyme covalent intermediate (Gastinel, L. N., Bignon, C., Misra, A. K., Hindsgaul, O., Shaper, J. H., and Joziasse, D. H. (2001) EMBO J. 20, 638-649). Highly ordered structures are described for complexes of alpha3GT with donor substrate, UDP-galactose, UDP- glucose, and two acceptor substrates, lactose and N-acetyllactosamine, at resolutions up to 1.46 A. Structural and calorimetric binding studies suggest an obligatory ordered binding of donor and acceptor substrates, linked to a donor substrate-induced conformational change, and the direct participation of UDP in acceptor binding. The monosaccharide-UDP bond is cleaved in the structures containing UDP-galactose and UDP-glucose, producing non-covalent complexes containing buried beta-galactose and alpha-glucose. The location of these monosaccharides and molecular modeling suggest that binding of a distorted conformation of UDP-galactose may be important in the catalytic mechanism of alpha3GT.
Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom.