title: PvdN Enzyme Catalyzes a Periplasmic Pyoverdine Modification.
abstract: Pyoverdines are high affinity siderophores produced by a broad range of pseudomonads to enhance growth under iron deficiency. They are especially relevant for pathogenic and mutualistic strains that inhabit iron-limited environments. Pyoverdines are generated from non-ribosomally synthesized highly modified peptides. They all contain an aromatic chromophore that is formed in the periplasm by intramolecular cyclization steps. Although the cytoplasmic peptide synthesis and side-chain modifications are well characterized, the periplasmic maturation steps are far from understood. Out of five periplasmic enzymes, PvdM, PvdN, PvdO, PvdP, and PvdQ, functions have been attributed only to PvdP and PvdQ. The other three enzymes are also regarded as essential for siderophore biosynthesis. The structure of PvdN has been solved recently, but no function could be assigned. Here we present the first in-frame deletion of the PvdN-encoding gene. Unexpectedly, PvdN turned out to be required for a specific modification of pyoverdine, whereas the overall amount of fluorescent pyoverdines was not altered by the mutation. The mutant strain grew normally under iron-limiting conditions. Mass spectrometry identified the PvdN-dependent modification as a transformation of the N-terminal glutamic acid to a succinamide. We postulate a pathway for this transformation catalyzed by the enzyme PvdN, which is most likely functional in the case of all pyoverdines.
authors.affiliation: From the Institute of Microbiology, Leibniz Universität Hannover, Herrenhäuser Straße 2, 30419 Hannover and.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Ringel
authors.affiliation: the Institute of Organic Chemistry, Leibniz Universität Hannover, Schneiderberg 1 B, 30167 Hannover, Germany.
authors.forename: Gerald
authors.initials: G
authors.lastname: Dräger
authors.affiliation: From the Institute of Microbiology, Leibniz Universität Hannover, Herrenhäuser Straße 2, 30419 Hannover and brueser@ifmb.uni-hannover.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Brüser
mesh_terms: D000577:Amides / Q000737:chemistry; D017353:Gene Deletion; D018698:Glutamic Acid / Q000737:chemistry; D009842:Oligopeptides / Q000235:genetics / Q000378:metabolism*; D019897:Periplasm / Q000201:enzymology* / Q000235:genetics; D033903:Periplasmic Proteins / Q000235:genetics / Q000378:metabolism*; D011551:Pseudomonas fluorescens / Q000201:enzymology* / Q000235:genetics; D013386:Succinates / Q000737:chemistry
chemical_list: D000577:Amides; D009842:Oligopeptides; D033903:Periplasmic Proteins; D013386:Succinates; D018698:Glutamic Acid; C042453:pyoverdin; C011116:succinamide
keywords: Pseudomonas fluorescens; decarboxylase; enzyme; iron; periplasmic tailoring; pyoverdines; pyridoxal phosphate; siderophore; siderophore maturation