title: Structural insights into the regulation of NADPH binding to reductase domains of nonribosomal peptide synthetases: A concerted loop movement model.
abstract: The termination module of nonribosomal peptide synthetases (NRPS) and polyketide synthases (PKS) offloads the final product as an acid (occasionally also accompanied by cyclization) upon hydrolysis by employing thioesterase domains (TE-domains). Reductase domains (R-domains) of short-chain dehydrogenase/reductase (SDR) family offer an alternative offloading mechanism by reducing 4'-phosphopantetheine (4'-PPant) arm-tethered peptidyl chain, a thioester, to an aldehyde or an alcohol. Recent studies have highlighted their functional importance, for instance in the glycopeptidolipid (GPL) biosynthesis of Mycobacterium smegmatis, where the resulting alcoholic group is the site for subsequent modifications such as glycosylations. The mechanistic understanding of how these R-domains function in the context of multi-modular NRPS and PKS is poorly understood. In this study, conformational differences in functionally important loops, not reported previously, were identified in a new crystal form of R-domain which may be relevant to functioning in the context of assembly-line NRPS and PKS enzymology. Here, we propose a concerted loop movement model that allows gating of cofactor binding to these enzymes, enabling the release of the final product only after the substrate has reached the active site during biosynthesis, and therefore distinct from a canonical single domain SDR family of enzymes.
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India.
authors.forename: Priyadarshan
authors.initials: P
authors.lastname: Kinatukara
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India.
authors.forename: Ketan D
authors.initials: KD
authors.lastname: Patel
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India.
authors.forename: Asfarul S
authors.initials: AS
authors.lastname: Haque
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India.
authors.forename: Raghavendra
authors.initials: R
authors.lastname: Singh
authors.affiliation: CSIR-Institute of Genomics and Integrative Biology, Delhi 110007, India; National Institute of Immunology, New Delhi 110067, India.
authors.forename: Rajesh S
authors.initials: RS
authors.lastname: Gokhale
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500007, India. Electronic address: sankar@ccmb.res.in.
authors.forename: Rajan
authors.initials: R
authors.lastname: Sankaranarayananan
mesh_terms: D001665:Binding Sites; D055162:Biocatalysis; D020134:Catalytic Domain; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D009249:NADP / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism; D010453:Peptide Synthases / Q000378:metabolism*; D048630:Polyketide Synthases / Q000378:metabolism; D011485:Protein Binding; D000072417:Protein Domains; D017434:Protein Structure, Tertiary
chemical_list: D009249:NADP; D048630:Polyketide Synthases; D010088:Oxidoreductases; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase
keywords: Catalytic loop; Gating loop; NRPS; Reductase domain; Short-chain dehydrogenase/reductase (SDR)