modified residue that can arise from different natural residues O-(L-isoglutamyl)-L-threonine 129.0425872802734375 129.1100006103515625 230.09027099609375 230.220001220703125 O(beta)-(gamma-glutamyl)threonine (2S,3R)-2-amino-3-([(4S)-4-amino-4-carboxybutanoyl]oxy)-propanoic acid C 9 H 14 N 2 O 5 none This is not an ester cross-link of peptides [JSG]. O3-(isoglutamyl)threonine 5-(threon-O3-yl)glutamate O-(L-isoglutamyl)-L-threonine T, X PSI-MOD (2S)-2-amino-5-([(1S,2R)-1-amino-1-carboxypropan-2-yl]oxy)-5-oxopentanoic acid hypothetical A protein modification that effectively converts an L-threonine residue to O-(L-isoglutamyl)-L-threonine, using free L-glutamine and releasing ammonia, or using a peptidyl L-glutamine and releasing ammonia. C 5 H 7 N 1 O 3 MOD:01979 crosslinked L-threonine residue