Biosynthesis of the Sesquiterpene Antibiotic Albaflavenone

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Overview

Title
Biosynthesis of the Sesquiterpene Antibiotic Albaflavenone
Contributors
Lin, Xin (creator)
Cane, David (director)
Basu, Amit (reader)
Sello, Jason (reader)
Brown University. Chemistry (sponsor)
Copyright Date
2009
Abstract
Streptomyces are Gram-positive, filamentous, soil-dwelling saprophytic bacteria that are the source of a vast array of bioactive secondary metabolites. The albaflavenone biosynthetic gene cluster in S. coelicolor A3(2) contains two ORFs, sco5222 and sco5223. The 1086-bp sco5222 gene encodes a protein of 361 amino acids (aa), which has been expressed in E. coli and characterized to catalyze the cyclization of farnesyl diphosphate (FPP) to epi-isozizaene. The sco5223 gene shares a four-nucleotide ATGA transcriptional overlap with sco5222 at its 5'-end, and was demonstrated to catalyze the two-step allylic oxidation of epi-isozizaene to albaflavenone through the intermediacy of an epimeric mixture of albaflavenols. The incubation experiments of labeled FPP and NPP with SCO5222 protein not only confirmed the intermediacy of (3R)-NPP in the cyclization mechanism, but also shed valuable new light on the stereochemistry of other reaction intermediates. In addition, the site-directed mutagenesis gave rise to the affected distribution of aberrant products, providing strong support for the presence of proposed intermediates. Recombinant SAV3032 in S. avermitilis has been expressed in E. coli and refolded from inclusion bodies, and the purified protein was characterized to catalyze the cyclization of FPP to epi-isozizaene. This result therefore implied the presence of albaflavenone biosynthesis pathway in S. avermitilis.
Keywords
albaflavenone
epi-isozizaene
sesquiterpene synthase
Streptomyces
Notes
Thesis (Ph.D.) -- Brown University (2009)
Extent
xv, 123 p.

Citation

Lin, Xin, "Biosynthesis of the Sesquiterpene Antibiotic Albaflavenone" (2009). Chemistry Theses and Dissertations. Brown Digital Repository. Brown University Library. https://repository.library.brown.edu/studio/item/bdr:79/

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