O-acylated residue modified L-serine residue O3-(poly-3-hydroxybutyrate)-L-serine (2S)-2-amino-3-[([(3R)-3-hydroxybutanoyl]oxy)-poly([(3R)-3-methyl-1-oxopropane-1,3-diyl]oxy)]propanoic acid A protein modification that effectively converts an L-serine residue to O3-(poly-3-hydroxybutyrate)-L-serine. MOD:01976 MOD_RES O3-poly(beta-hydroxybutyryl)lysine O3-(poly-3-hydroxybutyrate)-L-serine O3-poly(3-hydroxybutanoate)serine O3-poly(3-hydroxybutanoic acid)serine O3-poly(3-hydroxybutyrate)serine O3-poly(3-hydroxybutyric acid)serine O3-poly(beta-hydroxybutyrate)serine O3-poly[(R)-3-hydroxybutyrate]serine PSI-MOD S natural uniprot.ptm:PTM-0640