CDA: Calcium‐Dependent Peptide Antibiotics from <i>Streptomyces coelicolor</i> A3(2) Containing Unusual Residues

Abstract

Only in the presence of Ca2+ are ions channels formed by peptides of the group of calcium-dependent antibiotics (CDA). O-Phosphorylated D-3-hydroxyasparagine is one of the unusual residues in the microheterogeneous CDA undecapeptide lactone isolated from Streptomyces coelicolor A3(2) (see below). By combination of modern analytical methods, such as the coupling of a gas-phase sequencer to a mass spectrometer, a total of four structures could be elucidated from only a few milligrams of product.