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J. Bacteriol. doi:10.1128/JB.00826-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Characterization of the Saframycin A Gene Cluster from Streptomyces lavendulae NRRL 11002 Revealing a NRPS System for Assembling the Unusual Tetrapeptidyl Skeleton in an Iterative Manner

State Key Laboratory of Bioorganic and Natural Product Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Rd., Shanghai, 200032, China

^* To whom correspondence should be addressed. Email: gltang{at}mail.sioc.ac.cn. wliu{at}mail.sioc.ac.cn.

	Abstract

Saframycin A (SFM-A), produced by Streptomyces lavendulae NRRL 11002, belongs to the tetrahydroisoquinoline family of antibiotics and shares a core structurally similar to that of Ecteinascidin 743 (ET743), which is a highly potent antitumor drug isolated from a marine tunicate. In this study, the biosynthetic gene cluster for SFM-A was cloned and localized to a 62 kb contiguous DNA region. Sequence analysis revealed 30 genes that constitute the SFM-A gene cluster, encoding an unusual non-ribosomal peptide synthetase (NRPS) system and tailoring enzymes as well as regulatory and resistance proteins. Substrate prediction and in vitro characterization of the adenlyation specificities of this NRPS system supported that the last module acts in an iterative manner to form a tetrapeptidyl intermediate and the co-linearity rule does not apply. Although this is different to those proposed for the SFM-A analogs SFM-Mx1 and safracin B (SAC-B), based on the high similarity of these systems, it is likely they share a common mechanism of biosynthesis as we describe here. Construction of the biosynthetic pathway of SFM-Y3, an aminated SFM-A, was achieved in the SAC-B producer (Pseudomonas fluorescens). These findings not only shed new insight into tetrahydroisoquinoline biosynthesis, but also demonstrate the feasibility of engineering microorganisms to generate structurally more complex and biologically more active analogs by combinatorial biosynthesis.