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Publication Abstract from PubMed

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.

Structural basis of ordered binding of donor and acceptor substrates to the retaining glycosyltransferase, alpha-1,3-galactosyltransferase.,Boix E, Zhang Y, Swaminathan GJ, Brew K, Acharya KR J Biol Chem. 2002 Aug 2;277(31):28310-8. Epub 2002 May 14. PMID:12011052^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.