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Conformational study of bacterial lipopeptides: Refinement of the structure of iturin A in solution by two‐dimensional 1 H‐nmr and energy calculations
Author(s) -
Marion Dominique,
Genest Monique,
Caille Anita,
Peypoux Françoise,
Michel Georges,
Ptak Marius
Publication year - 1986
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360250111
Subject(s) - chemistry , lipopeptide , intramolecular force , crystallography , side chain , bacillus subtilis , pyridine , ring (chemistry) , stereochemistry , organic chemistry , bacteria , genetics , biology , polymer
Iturin A is a lipopeptide extracted from strains of Bacillus subtilis . Seven peptide residues form a cycle closed by a β‐amino acid carrying a hydrophobic tail. This compound is an antifungal and induces the formation of conducting pores in black lipid membranes. Two‐dimensional 1 H‐nmr was used for investigating its conformation in pyridine. A complete set of nuclear Overhauser effects (NOEs) was obtained from which interproton distances were deduced in a rather broad range of 2.2–4.2 Å. A special procedure was then used to optimize simultaneously experimental parameters and intramolecular energy calculated by semiempirical methods. A model of the conformation is proposed for the backbone for which there is an excellent coherence between NOEs, coupling constants, and intramolecular energy. The conformations of Asn, Gln, and Ser side chains appear to be much more flexible because of their interactions with the solvent. From this picture, iturin A seems to have a rather stiff ring surrounded by mobile side chains. Further studies of this lipopeptide and of other members of the family should enable us to approach some structure–activity relationships for this class of antibiotics.