DETERMINATION OF STRUCTURE AND CONFORMATION IN SOLUTION OF SYRINGOTOXIN, A LIPODEPSIPEPTIDE FROM PSEUDOMONAS-SYRINGAE PV SYRINGAE BY 2D NMRAND MOLECULAR-DYNAMICS

Strain B427 of Pseudomonas syringae pv. syringae, originally isolated from lemon, produces several bioactive lipodepsipeptides. The structur e of Syringotoxin (ST) and Syringopeptins (SPs) has been investigated in these last years. This paper reports the 2D NMR data collected in t he study of ST covalent structure. The study was performed in differen t solvents in order both to prevent aggregation and to completely char acterize the side chains features. These include the presence of commo n and less common aminoacids, which compose the macrocyclic ring and f atty acid side-chain moieties of ST. The nature and position in the mo lecule of the residues involved in the lactonic ring closure of ST hav e been identified with certainty. The interpretation of NOE data obtai ned in acetonitrile/water solution was performed by molecular dynamics calculations in vacuo. This procedure has allowed determination of th e nature and number of intramolecular hydrogen bonds and the predomina nt conformation of ST.