Structure of bovine α‐1,3‐galactosyltransferase and its complexes with UDP and DPGal inferred from molecular modeling

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Abstract
A homology model of α‐1,3‐galactosyltransferase (α‐1,3‐GalT), the retaining enzyme responsible for the formation of α‐galactosyl epitopes, has been developed by means of molecular modeling using the SpsA glycosyltransferase structure. A protein‐ligand docking approach was used to model α‐1,3‐GalT complexed with UDP and UDP‐Gal. The comparison of structural features found in the α‐1,3‐GalT homology model with available structural data on this class of enzymes revealed similarities in the UDP‐binding pocket. In the predicted structure of the complexes, the pyrophosphate interacts with the DVD motif (Asp‐225, Val‐226, and Asp‐227) of α‐1,3‐GalT through the Mn2+ cation. The uridine part of the UDP binds into the well‐defined cavity that consists of Phe‐134, Tyr‐139, Ile‐140, Val‐136, Arg‐194, Arg‐202, Lys‐209, Asp‐173, His‐218, and Thr‐137 in a conformation that is generally observed in the crystal structures of other glycosyltransferase complexes. Proteins 2001;44:428–434.