title: Partial In Vitro Reconstitution of an Orphan Polyketide Synthase Associated with Clinical Cases of Nocardiosis.
abstract: Although a few well-characterized polyketide synthases (PKSs) have been functionally reconstituted in vitro from purified protein components, the use of this strategy to decode "orphan" assembly line PKSs has not been described. To begin investigating a PKS found only in Nocardia strains associated with clinical cases of nocardiosis, we reconstituted in vitro its five terminal catalytic modules. In the presence of octanoyl-CoA, malonyl-CoA, NADPH, and S-adenosyl methionine, this pentamodular PKS system yielded unprecedented octaketide and heptaketide products whose structures were partially elucidated using mass spectrometry and NMR spectroscopy. The PKS has several notable features, including a "split, stuttering" module and a terminal reductive release mechanism. Our findings pave the way for further analysis of this unusual biosynthetic gene cluster whose natural product may enhance the infectivity of its producer strains in human hosts.
authors.affiliation: Department of Chemical Engineering, ‡Department of Chemistry, §Stanford Magnetic Resonance Laboratory, and ∥Stanford ChEM-H, Stanford University , Stanford, California 94305, United States.
authors.forename: James
authors.initials: J
authors.lastname: Kuo
authors.affiliation: Department of Chemical Engineering, ‡Department of Chemistry, §Stanford Magnetic Resonance Laboratory, and ∥Stanford ChEM-H, Stanford University , Stanford, California 94305, United States.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Lynch
authors.affiliation: Department of Chemical Engineering, ‡Department of Chemistry, §Stanford Magnetic Resonance Laboratory, and ∥Stanford ChEM-H, Stanford University , Stanford, California 94305, United States.
authors.forename: Corey W
authors.initials: CW
authors.lastname: Liu
authors.affiliation: Department of Chemical Engineering, ‡Department of Chemistry, §Stanford Magnetic Resonance Laboratory, and ∥Stanford ChEM-H, Stanford University , Stanford, California 94305, United States.
authors.forename: Xirui
authors.initials: X
authors.lastname: Xiao
authors.affiliation: Department of Chemical Engineering, ‡Department of Chemistry, §Stanford Magnetic Resonance Laboratory, and ∥Stanford ChEM-H, Stanford University , Stanford, California 94305, United States.
authors.forename: Chaitan
authors.initials: C
authors.lastname: Khosla
mesh_terms: D002853:Chromatography, Liquid; D066298:In Vitro Techniques; D009617:Nocardia Infections / Q000201:enzymology*; D019906:Nuclear Magnetic Resonance, Biomolecular; D048630:Polyketide Synthases / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D048630:Polyketide Synthases