BIOCHEMISTRY Correction for “Unraveling the iterative type I polyketide synthases hidden in Streptomyces,” by Bin Wang, Fang Guo, Chunshuai Huang, and Huimin Zhao, which was first published March 26, 2020; 10.1073/pnas.1917664117 (Proc. Natl. Acad. Sci. U.S.A. 117, 8449–8454).
The authors note that “The double-bond configuration in compound 2 is incorrect (Fig. 2). Specifically, in the study of the iterative T1PKS, AlnB, we conducted extensive in vivo and in vitro experiments. A pair of heptaketide and octaketide (major product, compound 2 in this manuscript) were identified in vivo, while in vitro the purified AlnB produced a pair of octaketide (major product, compound 2 in this manuscript) and nonaketide. All three products show similar UV-vis profiles with signature fine structures which indicate, based on the characterization of enediyne compounds as reported, that the polyene parts in all three structures are not conjugated with the carbonyl (carboxylic) groups, adopting either polyene-CαH2-COOH (revised, correct structure) or polyene-CβH2-CαH2-COOH (incorrect structure). As we detected only the major product octaketide 2 then, the UV-vis profile and HRMS data did not enable us to distinguish between the two possibilities albeit great efforts were spent to purify the octaketide from the in vivo experiment. The polyene compound characterization was not solid, but as the main discovery in this manuscript is the iterative T1PKSs in bacteria, we therefore tentatively hypothesized the structure as polyene-CβH2-CαH2-COOH, which is reasonable by itself in the biosynthesis. However, we now have three intermediates from late stages which suggest a polyene-CαH2-COOH structure. Another piece of supporting evidence is that we verified β,γ-double bond carboxylic acids (-CγH=CβH-CαH2-COOH) as the true intermediates rather than canonical α,β-double bond (-CβH=CαH-COOH), supporting the hypothesis that the octaketide 2 together with the heptaketide and nonaketide are all synthesized as polyene-CαH2-COOH rather than polyene-CβH2-CαH2-COOH.”
Due to the above error, Fig. 2 appeared incorrectly. The corrected figure and its legend appear below.
Summary of the heterologous expression experiments for the T1PKS monomodules. The single PKS modules were heterologously expressed except for class G2 in which a KSIII gene immediately downstream was also included. The module compositions of each class are shown in Fig. 1C, while the BGC designations are shown in SI Appendix, Table S2. The diverse branched/nonbranched linear polyketide intermediates indicate the iterative nature of the corresponding PKS modules; e.g., class G4 employs a CoA-ligase to load 3- or 4-hydroxybenzoic acid as a starter unit and then runs the KS-AT-DH-KR-ACP for seven iterations by using malonyl-CoA as the extender unit and finally releases the octaketide polyenomycins by thioesterase.
Fig. S2 in the SI Appendix also appeared incorrectly. The SI Appendix has been corrected online.
In addition, the authors note that nucleotide sequence data for the aln and cit BGCs are available in the Third Party Annotation Section of the DDBJ/ENA/GenBank databases. The accession number is TPA: BK059189–BK059190.
The online version has been corrected.
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December 24, 2021 at 03:33AM
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Correction for Wang et al., Unraveling the iterative type I polyketide synthases hidden in Streptomyces - pnas.org
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