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

Strain B427 of Pseudomonas syringae pv. syringae, originally isolated from lemon, produces several bioactive lipodepsipeptides. The structure of Syringotoxin (ST) and Syringopeptins (SPs) has been investigated in these last years. This paper reports the 2D NMR data collected in the study of ST covalent structure. The study was performed in different solvents in order both to prevent aggregation and to completely characterize the side chains features. These include the presence of common and less common aminoacids, which compose the macrocyclic ring and fatty acid side-chain moieties of ST. The nature and position in the molecule of the residues involved in the lactonic ring closure of ST have been identified with certainty. The interpretation of NOE data obtained in acetonitrile/water solution was performed by molecular dynamics calculations in vacuo. This procedure has allowed determination of the nature and number of intramolecular hydrogen bonds and the predominant conformation of ST.