ester crosslinked residues crosslinked residues with loss of ammonia O-(L-isoglutamyl)-L-threonine (Gln-Thr) (2S)-2-amino-5-([(1S,2R)-1-amino-1-carboxypropan-2-yl]oxy)-5-oxopentanoic acid (2S,3R)-2-amino-3-([(4S)-4-amino-4-carboxybutanoyl]oxy)-propanoic acid -17.026548385620117188 -17.030000686645507812 212.0797119140625 212.1999969482421875 5-(threon-O3-yl)glutamate A protein modification that effectively cross-links an L-threonine residue and an L-glutamine residue with an ester bond releasing ammonia to form O-(L-isoglutamyl)-L-threonine. C 0 H -3 N -1 O 0 C 9 H 12 N 2 O 4 Cross-link 2. MOD:01952 O(beta)-(gamma-glutamyl)threonine O-(L-isoglutamyl)-L-threonine O3-(isoglutamyl)threonine PSI-MOD Q, T natural O-(L-isoglutamyl)-L-threonine crosslinked L-glutamine residue crosslinked L-threonine residue