PvdN enzyme catalyzes a periplasmic pyoverdine modification

authored by

Michael T. Ringel, Gerald Dräger, Thomas Brüser

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.

Organisation(s)

Institute of Microbiology
Institute of Organic Chemistry

Type

Article

Journal

Journal of Biological Chemistry

Volume

291

Pages

23929-23938

No. of pages

10

ISSN

0021-9258

Publication date

11.11.2016

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Biochemistry, Molecular Biology, Cell Biology

Electronic version(s)

https://doi.org/10.1074/jbc.M116.755611 (Access: Open)