Nosiheptide is a member of a sulphur-rich heterocyclic peptides class. All share a macrocylic core, consisting of a nitrogen containing, six-membered ring central to dehydroamino acids and a subset of five member ring structures including thiazoles, thiazolines and oxazoles. The main characteristic of the nosiheptide structure is a general tendency to be more oxidized than the thiostrepton one. No thiazoline, or hydrogenated quinaldic precursor nor tetrahydropyridine rings are present in nosiheptide. All the corresponding rings are unsaturated. Nosiheptide possess an indolic acid ring system that is appended to the side chains of the Ser/Cys and a central 6-membered nitrogen heterocycle produced by cyclization between two corresponding dehydroalanine acids with incorporation of an adjacent carbonyl group. Thiazole formation is by nucleophilic addition of each Cys side chain to the proceeding carbonyl group followed by dehydration and dehydrogenation. HERE, NOSIHEPTIDE IS REPRESENTED BY GROUPING TOGETHER THE SEQUENCE (SEQRES) AND THE ONE LIGAND (HET) NO1.
NOSIHEPTIDE IS A HETROCYCLIC THIOPEPTIDE, CONSISTING OF FIVE THIAZOLES AND ONE 3-HYDROXYPYRIDINE RINGS. A MODIFIED INDOLE RING NO1(14) IS LINKED VIA THE SIDE CHAINS OF 3-HYDROXY 3GL(6) AND CYS(8). THE OBSERVED C-TERMINAL AMINO GROUP NH2(13) IS LIKELY TO BE A POST-TRANSLATIONAL DECARBOXYLATED REMNANT OF A SER C-TERMINAL RESIDUE