This Article Full Text (PDF) Other Versions of this Article: AAC.01053-07v1 52/5/1686    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Eys, S. Articles by Schinko, E. Search for Related Content PubMed PubMed Citation Articles by Eys, S. Articles by Schinko, E.

 Previous Article  |  Next Article 

Antimicrob. Agents Chemother. doi:10.1128/AAC.01053-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Three Thioesterases are Involved in the Biosynthesis of Phosphinothricin Tripeptide in Streptomyces viridochromogenes Tü494

Mikrobiologie/Biotechnologie, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany; Fachhochschule Esslingen – Hochschule für Technik, Angewandte Naturwissenschaften –Biotechnologie, Kanalstraße 33, 73728 Esslingen, Germany

^* To whom correspondence should be addressed. Email: evah{at}biotech.uni-tuebingen.de.

	Abstract

Phosphinothricin tripeptide (PTT) is a peptide antibiotic produced by Streptomyces viridochromogenes Tü494, which is synthesized by non-ribosomal peptide synthetases. The PTT biosynthetic gene cluster contains three peptide synthetase genes: phsA, phsB and phsC. Each of these peptide synthetases comprises only one module. In neither PhsB nor PhsC is a typical C-terminal thioesterase domain present. In contrast, a single thioesterase GXSXG motif has been identified in the N-terminus of the first peptide synthetase PhsA. In addition, two external thioesterase genes, theA and theB, are located within the PTT biosynthetic gene cluster. To analyze the thioesterase function as well as the assembly of the peptide synthetases within PTT biosynthesis, several mutants were generated and analyzed. A phsA deletion mutant (MphsA) was complemented with two different phsA constructs carrying mutations in the thioesterase motif. In one construct, the thioesterase motif comprising 45 amino acids of phsA were deleted. In the second construct, the conserved serine residue of the GXSXG motif was replaced by an alanine. In both cases, complementation of MphsA did not restore PTT biosynthesis, revealing that the thioesterase motif in the N-terminus of PhsA is required for PTT production. In contrast, TheA and TheB might have editing functions, as an interruption of the theA and theB genes led to reduced PTT production, whereas an overexpression of both genes in the wild-type enhanced PTT yield. The presence of an active single thioesterase motif in the N-terminus of PhsA points to a novel mechanism of product release.