Journal of Microbiology

Research Support, Non-U.S. Gov't

Cloning and Analysis of a Type II Polyketide Synthase Gene Cluster from Streptomyces toxytricini NRRL 15,443: Anna Yoo , Atanas V. Demirev , Ji Seon Lee , Sang Dal Kim , Doo Hyun Nam; J. Microbiol. 2006;44(6):649-654.; DOI: https://doi.org/2462 [pii]

Abstract: A standard type II polyketide synthase (PKS) gene cluster was isolated while attempting to clone the biosynthetic gene for lipstatin from Streptomyces toxytricini NRRL 15,443. This result was observed using a Southern blot of a PstI-digested S. toxytricini chromosomal DNA library with a 444 bp amplified probe of a ketosynthase (KS) gene fragment. Four open reading frames [thioesterase (TE), β-ketoacyl systhase (KAS), chain length factor (CLF), and acyl carrier protein (ACP)], were identified through the nucleotide sequence determination and analysis of a 4.5 kb cloned DNA fragment. In order to confirm the involvement of a cloned gene in lipstatin biosynthesis, a gene disruption experiment for the KS gene was performed. However, the resulting gene disruptant did not show any significant difference in lipstatin production when compared to wild-type S. toxytricini. This result suggests that lipstatin may not be synthesized by a type II PKS.

Nucleotide sequence analysis of a second set of the polyketide synthase β-ketoacyl synthase and chain length factor genes from the salinomycin-producing streptomyces albus: Hyun, Chang Gu , Park, Kwan Hyung , Hutchinson, C. Richard , Suh, Joo Won; J. Microbiol. 1997;35(1):40-46.

Abstract: The pWHM220 cosmid with a 24-kb insert cloned from Streptomyces albus ATCC 21838 induces the biosynthesis of a polyether antibiotic similar to salinomycin in Streptomyces invidans. We have analyzed this region by DNA sequencing as well as Southern blot hybridization with type I and type II polyketide synthase (PKS) probes. Surprisingly, we found another set of type II SKS genes only 10-kb from the original PKS genes, salABCDE. The DNA sequence revealed two complete open reading frames (ORFs) named salB2 and salC2, and one partial ORF that does not resemble any known DNA or deduced protein sequence. The salC2 should code for chain length determining factor while the deduced amino acid sequence encoded by salB2 exhibits high similarity to β-ketoacyl synthase from different PKS gene clusters. The highest identity was found for β-keetoacyl synthesis from S. argillaceus (MtmP. 59.1% identity), the mithramycin producer and from S. venezuelae ISP5230 (JadA, 52.3% identity), the jadomycin producer. The SalC2 protein clearly resembles its counterparts in order aromatic PKS gene clusters that are believed to influence the length of the polyketide chain. The highest identities observed were to that of S. argillaceus (MtmK, 62.3%) and S. venezuelae ISP 5230 (JadB, 55.1%) proteins, Moreover, the deduced amino acid sequences of the salB2 and salC2 products were 29.0% identical.

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