Biosynthesis of the Tricyclic Aromatic Type II Polyketide Rishirilide: New Potential Third Ring Oxygenation after Three Cyclization Steps

Abstract

Rishirilides are a group of PKS II secondary metabolites produced by Streptomyces bottropensis Gö C4/4. Biosynthetic studies in the past have elucidated early and late steps of rishirilide biosynthesis. This work is aiming to solve the remaining steps in the rishirilide biosynthesis. Inactivation of the cyclase gene rslC3 in Streptomyces bottropensis resulted in an interruption of rishirilide production. Instead, accumulation of the tricyclic aromatic galvaquinones was observed. Similar results were observed after deletion of rslO4. Closer inspection into RslO4 crystal structure in addition to site-directed mutagenesis and molecular dynamic simulations revealed that RslO4 might be responsible for quinone formation on the third ring. The RslO1 three-dimensional structure shows a high similarity to FMN-dependent luciferase-like monooxygenases such as the epoxy-forming MsnO8 which acts with the flavin reductase MsnO3 in mensacarcin biosynthesis in the same strain. The high sequence similarity between RslO2 and MsnO3 suggests that RslO2 provides RslO1 with reduced FMN to form an epoxide that serves as substrate for RslO5.

Discovery, isolation, heterologous expression and mode-of-action studies of the antibiotic polyketide tatiomicin from Amycolatopsis sp. DEM30355

“…DEM30355 was examined using the secondary metabolite analysis software AntiSMASH 6.0.1 21 . Of the 31 biosynthetic gene clusters (BGCs) detected, a PKS cluster was identified showing moderate overall similarity (81%) to that which encodes for rishirilides A and B 22 – 26 . These compounds are anthracenone polyketides, originally isolated from Streptomyces rishiriensis OFR-1056, with no reported antibiotic activity.…”

“…Based on a comparison between the tatiomicin and rishirilide BGCs 22 – 26 we propose the following biosynthetic pathway operates for the assembly of tatiomicin ( 3 ) (See ESI). The modular type I polyketide synthase TatS1 is likely responsible for the biosynthesis of the polyketide starter unit, cis -crotonyl-ACP, which is then elongated via the attachment of eight malonyl-CoA by minimal PKS enzymes TatK1, TatK2, and TatK3.…”

Discovery, Isolation, Heterologous Expression and Mode-of Action Studies of the Antibiotic Polyketide Tatiomicin from Amycolatopsis sp. DEM30355

“…DEM30355 was examined using the secondary metabolite analysis software AntiSMASH 6.0.1 21 . Of the 31 biosynthetic gene clusters (BGCs) detected, a PKS cluster was identified showing moderate overall similarity (81%) to that which encodes for rishirilides A and B [22][23][24][25][26] . These compounds are anthracenone polyketides, originally isolated from Streptomyces rishiriensis OFR-1056, with no reported antibiotic activity.…”

Evaluation of the function of a luciferase-like monooxygenase homologue in 4,4´-dithiodibutyric acid catabolism in Rhodococcus erythropolis MI2

“…The bacterial luciferase from Vibrio harveyi is a flavin-containing monooxygenase that oxidizes aldehyde to a carboxylic acid while emitting visible light [39]. Alali et al [40] reported that FMN-dependent LLM involved in the production of rishirilides which are a group of PKS II secondary metabolites produced by Streptomyces bottropensis. Li et al [41] found that four LLM class flavin-dependent oxidoreductase coding genes.…”