Premium
Crystal structure of GlcAT‐S, a human glucuronyltransferase, involved in the biosynthesis of the HNK‐1 carbohydrate epitope
Author(s) -
Shiba Tomoo,
Kakuda Shinako,
Ishiguro Masaji,
Morita Ippei,
Oka Shogo,
Kawasaki Toshisuke,
Wakatsuki Soichi,
Kato Ryuichi
Publication year - 2006
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.21118
Subject(s) - chemistry , substrate (aquarium) , psychology , ecology , biology
The HNK‐1 carbohydrate epitope is found in various neural cell adhesion molecules. Two glucuronyltransferases (GlcAT‐P and GlcAT‐S) are involved in the biosynthesis of HNK‐1 carbohydrate. Our previous study on the crystal structure of GlcAT‐P revealed the reaction and substrate recognition mechanisms of this enzyme. Comparative analyses of the enzymatic activities of GlcAT‐S and GlcAT‐P showed that there are notable differences in the acceptor substrate specificities of these enzymes. To elucidate differences between their specificities, we now solved the crystal structure of GlcAT‐S. Residues interacting with UDP molecule, which is a part of the donor substrate, are highly conserved between GlcAT‐P and GlcAT‐S. On the other hand, there are some differences between these proteins in the manner they recognize their respective acceptor substrates. Phe245, one of the most important GlcAT‐P residues for the recognition of acceptors, is a tryptophan in GlcAT‐S. In addition, Val320, which is located on the C‐terminal long loop of the neighboring molecule in the dimer and critical in the recognition of the acceptor sugar molecule by the GlcAT‐P dimer, is an alanine in GlcAT‐S. These differences play key roles in establishing the distinct specificity for the acceptor substrate by GlcAT‐S, which is further supported by site‐directed mutagenesis of GlcAT‐S and a computer‐aided model building of GlcAT‐S/substrate complexes. Proteins 2006. © 2006 Wiley‐Liss, Inc.