modified L-proline residue cis-peptidyl-L-proline 0.0 0.0 A protein modification that effectively specifies the boundary conformation of two adjacent source amino acid residues, the second (C-term side) being a L-proline, where the carbonyl group of the amide bond of the N-side of the L-proline is positioned such that the organodiyl group is in the cis orientation (omega=0) C 0 H 0 N 0 O 0 MOD:02029 PSI-MOD X, P natural