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X‐ray crystal structure of rabbit N ‐acetylglucosaminyltransferase I: catalytic mechanism and a new protein superfamily
Author(s) -
Ünligil Uluĝ M.,
Zhou Sihong,
Yuwaraj Sivashankary,
Sarkar Mohan,
Schachter Harry,
Rini James M.
Publication year - 2000
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/19.20.5269
Subject(s) - biology , bacillus subtilis , transferase , threading (protein sequence) , glycosyltransferase , biochemistry , glycan , escherichia coli , protein domain , peptide sequence , protein structure , sequence alignment , aquifex aeolicus , enzyme , genetics , glycoprotein , gene , bacteria
N ‐acetylglucosaminyltransferase I (GnT I) serves as the gateway from oligomannose to hybrid and complex N ‐glycans and plays a critical role in mammalian development and possibly all metazoans. We have determined the X‐ray crystal structure of the catalytic fragment of GnT I in the absence and presence of bound UDP‐GlcNAc/Mn 2+ at 1.5 and 1.8 Å resolution, respectively. The structures identify residues critical for substrate binding and catalysis and provide evidence for similarity, at the mechanistic level, to the deglycosylation step of retaining β‐glycosidases. The structuring of a 13 residue loop, resulting from UDP‐GlcNAc/Mn 2+ binding, provides an explanation for the ordered sequential ‘Bi Bi’ kinetics shown by GnT I. Analysis reveals a domain shared with Bacillus subtilis glycosyltransferase SpsA, bovine β‐1,4‐galactosyl transferase 1 and Escherichia coli N ‐acetylglucosamine‐1‐phosphate uridyltransferase. The low sequence identity, conserved fold and related functional features shown by this domain define a superfamily whose members probably share a common ancestor. Sequence analysis and protein threading show that the domain is represented in proteins from several glycosyltransferase families.