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  • Properties of a "Split-and-Stuttering" Module of an Assembly Line Polyketide Synthase JOURNAL OF ORGANIC CHEMISTRY Guzman, K. M., Yuet, K. P., Lynch, S. R., Liu, C. W., Khosla, C. 2021; 86 (16): 11100-11106

    Abstract

    Notwithstanding the "one-module-one-elongation-cycle" paradigm of assembly line polyketide synthases (PKSs), some PKSs harbor modules that iteratively elongate their substrates through a defined number of cycles. While some insights into module iteration, also referred to as "stuttering", have been derived through in vivo and in vitro analysis of a few PKS modules, a general understanding of the mechanistic principles underlying module iteration remains elusive. This report serves as the first interrogation of a stuttering module from a trans-AT subfamily PKS that is also naturally split across two polypeptides. Previous work has shown that Module 5 of the NOCAP (nocardiosis associated polyketide) synthase iterates precisely three times in the biosynthesis of its polyketide product, resulting in an all-trans-configured triene moiety in the polyketide product. Here, we describe the intrinsic catalytic properties of this NOCAP synthase module. Through complementary experiments in vitro and in E. coli, the "split-and-stuttering" module was shown to catalyze up to five elongation cycles, although its dehydratase domain ceased to function after three cycles. Unexpectedly, the central olefinic group of this truncated product had a cis configuration. Our findings set the stage for further in-depth analysis of a structurally and functionally unusual PKS module with contextual biosynthetic plasticity.

    View details for DOI 10.1021/acs.joc.1c00120

    View details for Web of Science ID 000687851300016

    View details for PubMedID 33755455

    View details for PubMedCentralID PMC8380650