RESIDUE A5N 20 CONECT N 3 CA HN1 HN2 CONECT CA 4 N C CB HA CONECT C 3 CA O OXT CONECT O 1 C CONECT CB 4 CA CG HB1C HB2C CONECT CG 3 CB OD1 ND2 CONECT OD1 2 CG C1 CONECT ND2 2 CG HD2 CONECT C1 3 OD1 O2 O3 CONECT O2 1 C1 CONECT O3 2 C1 H3 CONECT OXT 2 C HXT CONECT H3 1 O3 CONECT HD2 1 ND2 CONECT HB1C 1 CB CONECT HB2C 1 CB CONECT HA 1 CA CONECT HN1 1 N CONECT HN2 1 N CONECT HXT 1 OXT END HET A5N 20 HETNAM A5N O-carboxy-4-imino-L-homoserine FORMUL A5N C5 H8 N2 O5