Biosynthesis of Versipelostatin: Identification of an Enzyme-Catalyzed [4+2]-Cycloaddition Required for Macrocyclization of Spirotetronate-Containing Polyketides

Versipelostatin (VST) is an unusual 17-membered macrocyclic polyketide product that contains a spirotetronate skeleton. In this study, the entire VST biosynthetic gene cluster (<i>vst</i>) spanning 108 kb from <i>Streptomyces versipellis</i> 4083-SVS6 was identified by heterologous expression using a bacterial artificial chromosome vector. Here, we demonstrate that an enzyme, VstJ, catalyzes the stereoselective [4+2]-cycloaddition between the conjugated diene and the exocyclic olefin of a newly identified tetronate-containing intermediate to form the spirotetronate skeleton during VST biosynthesis

MICs of β-lactams for <i>P</i>. <i>aeruginosa</i> NCGM1984 and <i>E</i>. <i>coli</i> transformants with <i>bla</i>_IMP-1 and <i>bla</i>_IMP-34.

<p>MICs of β-lactams for <i>P</i>. <i>aeruginosa</i> NCGM1984 and <i>E</i>. <i>coli</i> transformants with <i>bla</i>_IMP-1 and <i>bla</i>_IMP-34.</p

Kinetic parameters of the β-lactamases IMP-1 and IMP-34 with various substrates.

<p>Kinetic parameters of the β-lactamases IMP-1 and IMP-34 with various substrates.</p

Genomic islands containing class 1 integrons in <i>Pseudomonas aeruginosa</i> NCGM1984.

<p>(A) Genomic island containing integrons A and B. The genomic island was inserted between NCGM1984_2402 (PA2752 in the complete genome of <i>P</i>. <i>aeruginosa</i> PAO1: accession no.AE004091) and NCGM1984_2462 (PA2749). (B) Genomic island containing integron C. The genomic island was inserted between NCGM1984_4147 (PA1181) and NCGM1984_4144 (PA1179). (C) The genomic structure of integrons A and C. The structure of integron A was identical to that of integron C. These integrons contained <i>bla</i>_IMP-34. The red arrow indicates <i>bla</i>_IMP-34. Blue arrows indicate IRi and IRt. Green arrows indicate direct repeats. (D) Genomic structure of integron B. Blue arrows indicate IRi and IRt. Green arrows indicate direct repeats.</p