Assembly line biosynthesis of anguibactin, a siderophore from the fish pathogen Vibrio anguillarum

Abstract

The siderophore anguibactin is an important component of the pJM 1 plasmidmediated iron uptake system that is essential for virulence in this pathogenic vibrio. Genetic and physiological analysis has led us to the identification and cloning of genes encoded on the pJM 1 plasmid that play an essential role in anguibactin biosynthesis. DNA sequence and protein analysis revealed that these genes encode polypeptides which possess domains found in nonribosomal peptide synthetases (NRPSs), originally identified as components of the biosynthetic machinery for the synthesis of antibiotics in Gram-positive bacteria. These proteins have been named AngB, AngM, AngN, and AngR and possess modules that could be involved in one or more of the following reactions during the biosynthesis of anguibactin: peptidyl carrier protein (PCP), involved in thioester formation; condensation (C), intervening in peptide bond formation, cyclization (Cy), involved in both condensation and heterocycle formation and adenylation (A), which is responsible for substrate activation. AngB is an isochorismate lyase that also operates as an aryl carrier (ArCP) protein during siderophore assembly. The combination of our in vivo genetic and in vitro biochemical approaches has resulted in the elucidation of the mechanism of anguibactin biosynthesis and its contribution to the virulence repertoire of this fish pathogen.