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Oligosaccharyltransferase is highly specific for the hydroxy amino acid in Asn‐Xaa‐Thr/Ser
Author(s) -
Breuer Wilhelm,
Klein Roger A,
Hardt Birgit,
Bartoschek Achim,
Bause Ernst
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02641-2
Subject(s) - chemistry , threonine , stereochemistry , asparagine , amino acid , stereospecificity , tripeptide , serine , cysteine , peptide , enzyme , biochemistry , catalysis
Pig liver oligosaccharyltransferase (OST), which is involved in the en bloc transfer of the Dol‐PP‐linked GlcNAc 2 ‐Man 9 ‐Glc 3 precursor on to asparagine residues in the Asn‐Xaa‐Thr/Ser sequence, is highly stereospecific for the conformation of the 3‐carbon atom in the hydroxy amino acid. Moreover, substitution of the hydroxy group by either SH as in cysteine, or NH 2 as in β,γ‐diamino‐butanoic acid as reported previously [Bause, E. et al., Biochem. J. 312 (1995) 979–985], followed by the determination of the pH optimum for enzymatic activity, indicates that neither a negative nor a positive charge in the hydroxy amino acid position is tolerated by the enzyme. Binding of the threonine β‐methyl group by OST is also specific, with serine, L ‐ threo ‐β‐hydroxynorvaline and L ‐β‐hydroxynorleucine containing tripeptides all bound much less efficiently than the threonine peptide itself. The data are interpreted in terms of a highly stereospecific hydrophobic binding pocket for the threonine CH 3 ‐CH(OH) group.