2AEC

Crystal Structure of Human M340H-Beta1,4-Galactosyltransferase-I (M340H-B4GAL-T1) in Complex with GlcNAc-beta1,2-Man-alpha1,6-Man-beta-OR

Summary for 2AEC

• Entry DOI: 10.2210/pdb2aec/pdb
• Related: 1O0R 1TVY 1TW1 1TW5 2AE7 2AES 2AGD 2AH9
• Descriptor: Beta-1,4-galactosyltransferase 1, 2-acetamido-2-deoxy-beta-D-glucopyranose-(1-2)-alpha-D-mannopyranose-(1-6)-beta-D-mannopyranose, MANGANESE (II) ION, ... (9 entities in total)
• Functional Keywords: beta1, 4-galactosyltransferase-i; trisaccharide; closed conformation; mutant, transferase
• Biological source: Homo sapiens (human)
• Total number of polymer chains: 3
• Total formula weight: 103903.86

Authors

Ramasamy, V.,Ramakrishnan, B.,Boeggeman, E.,Ratner, D.M.,Seeberger, P.H.,Qasba, P.K. (deposition date: 2005-07-22, release date: 2005-10-04, Last modification date: 2024-10-09)

Primary citation

Ramasamy, V.,Ramakrishnan, B.,Boeggeman, E.,Ratner, D.M.,Seeberger, P.H.,Qasba, P.K.
Oligosaccharide Preferences of beta1,4-Galactosyltransferase-I: Crystal Structures of Met340His Mutant of Human beta1,4-Galactosyltransferase-I with a Pentasaccharide and Trisaccharides of the N-Glycan Moiety
J.Mol.Biol., 353:53-67, 2005

PubMed Abstract: beta-1,4-Galactosyltransferase-I (beta4Gal-T1) transfers galactose from UDP-galactose to N-acetylglucosamine (GlcNAc) residues of the branched N-linked oligosaccharide chains of glycoproteins. In an N-linked biantennary oligosaccharide chain, one antenna is attached to the 3-hydroxyl-(1,3-arm), and the other to the 6-hydroxyl-(1,6-arm) group of mannose, which is beta-1,4-linked to an N-linked chitobiose, attached to the aspargine residue of a protein. For a better understanding of the branch specificity of beta4Gal-T1 towards the GlcNAc residues of N-glycans, we have carried out kinetic and crystallographic studies with the wild-type human beta4Gal-T1 (h-beta4Gal-T1) and the mutant Met340His-beta4Gal-T1 (h-M340H-beta4Gal-T1) in complex with a GlcNAc-containing pentasaccharide and several GlcNAc-containing trisaccharides present in N-glycans. The oligosaccharides used were: pentasaccharide GlcNAcbeta1,2-Manalpha1,6 (GlcNAcbeta1,2-Manalpha1,3)Man; the 1,6-arm trisaccharide, GlcNAcbeta1,2-Manalpha1,6-Manbeta-OR (1,2-1,6-arm); the 1,3-arm trisaccharides, GlcNAcbeta1,2-Manalpha1,3-Manbeta-OR (1,2-1,3-arm) and GlcNAcbeta1,4-Manalpha1,3-Manbeta-OR (1,4-1,3-arm); and the trisaccharide GlcNAcbeta1,4-GlcNAcbeta1,4-GlcNAc (chitotriose). With the wild-type h-beta4Gal-T1, the K(m) of 1,2-1,6-arm is approximately tenfold lower than for 1,2-1,3-arm and 1,4-1,3-arm, and 22-fold lower than for chitotriose. Crystal structures of h-M340H-beta4Gal-T1 in complex with the pentasaccharide and various trisaccharides at 1.9-2.0A resolution showed that beta4Gal-T1 is in a closed conformation with the oligosaccharide bound to the enzyme, and the 1,2-1,6-arm trisaccharide makes the maximum number of interactions with the enzyme, which is in concurrence with the lowest K(m) for the trisaccharide. Present studies suggest that beta4Gal-T1 interacts preferentially with the 1,2-1,6-arm trisaccharide rather than with the 1,2-1,3-arm or 1,4-1,3-arm of a bi- or tri-antennary oligosaccharide chain of N-glycan.

PubMed: 16157350
DOI: 10.1016/j.jmb.2005.07.050

Experimental method

X-RAY DIFFRACTION (2 Å)