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May DS, Chen WL, Lantvit DD, Zhang X, Krunic A, Burdette JE, Eustaquio A, Orjala J. Merocyclophanes C and D from the Cultured Freshwater Cyanobacterium Nostoc sp. (UIC 10110). JOURNAL OF NATURAL PRODUCTS 2017; 80:1073-1080. [PMID: 28252962 PMCID: PMC5898374 DOI: 10.1021/acs.jnatprod.6b01175] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Merocyclophanes C and D (1 and 2) were isolated from the cell extract of the cultured cyanobacterium UIC 10110. The structures were determined by one-dimensional nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry and confirmed by 2D NMR techniques. The absolute configurations were determined using electronic circular dichroism spectroscopy. Merocyclophanes C and D represent the first known analogues of the merocyclophane core structure, a recently discovered scaffold of [7,7] paracyclophanes characterized by an α-branched methyl at C-1/C-14; 1 and 2 showed antiproliferative activity against the MDA-MB-435 cell line with IC50 values of 1.6 and 0.9 μM, respectively. Partial 16S analysis determined UIC 10110 to be a Nostoc sp., and it was found to clade with UIC 10062 Nostoc sp., the only other strain known to produce merocyclophanes. The genome of UIC 10110 was sequenced, and a biosynthetic gene cluster was identified that is proposed to encode type I and type III polyketide synthases that are potentially responsible for production of the merocyclophanes; however, further experiments will be required to verify the true function of the gene cluster. The gene cluster provides a genetic basis for the observed structural differences of the [7,7] paracyclophane core structures.
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Affiliation(s)
- Daniel S May
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Wei-Lun Chen
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Daniel D Lantvit
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Xiaoli Zhang
- Center for Biostatistics, The Ohio State University, Columbus, Ohio 43210, United States
| | - Aleksej Krunic
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Joanna E Burdette
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Alessandra Eustaquio
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Jimmy Orjala
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois 60612, United States
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Satou R, Miyanaga A, Ozawa H, Funa N, Katsuyama Y, Miyazono KI, Tanokura M, Ohnishi Y, Horinouchi S. Structural basis for cyclization specificity of two Azotobacter type III polyketide synthases: a single amino acid substitution reverses their cyclization specificity. J Biol Chem 2013; 288:34146-34157. [PMID: 24100027 DOI: 10.1074/jbc.m113.487272] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Type III polyketide synthases (PKSs) show diverse cyclization specificity. We previously characterized two Azotobacter type III PKSs (ArsB and ArsC) with different cyclization specificity. ArsB and ArsC, which share a high sequence identity (71%), produce alkylresorcinols and alkylpyrones through aldol condensation and lactonization of the same polyketomethylene intermediate, respectively. Here we identified a key amino acid residue for the cyclization specificity of each enzyme by site-directed mutagenesis. Trp-281 of ArsB corresponded to Gly-284 of ArsC in the amino acid sequence alignment. The ArsB W281G mutant synthesized alkylpyrone but not alkylresorcinol. In contrast, the ArsC G284W mutant synthesized alkylresorcinol with a small amount of alkylpyrone. These results indicate that this amino acid residue (Trp-281 of ArsB or Gly-284 of ArsC) should occupy a critical position for the cyclization specificity of each enzyme. We then determined crystal structures of the wild-type and G284W ArsC proteins at resolutions of 1.76 and 1.99 Å, respectively. Comparison of these two ArsC structures indicates that the G284W substitution brings a steric wall to the active site cavity, resulting in a significant reduction of the cavity volume. We postulate that the polyketomethylene intermediate can be folded to a suitable form for aldol condensation only in such a relatively narrow cavity of ArsC G284W (and presumably ArsB). This is the first report on the alteration of cyclization specificity from lactonization to aldol condensation for a type III PKS. The ArsC G284W structure is significant as it is the first reported structure of a microbial resorcinol synthase.
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Affiliation(s)
- Ryutaro Satou
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Akimasa Miyanaga
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Hiroki Ozawa
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Nobutaka Funa
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Yohei Katsuyama
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Ken-Ichi Miyazono
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Masaru Tanokura
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Yasuo Ohnishi
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
| | - Sueharu Horinouchi
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
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Kim SY, Colpitts CC, Wiedemann G, Jepson C, Rahimi M, Rothwell JR, McInnes AD, Hasebe M, Reski R, Sterenberg BT, Suh DY. Physcomitrella PpORS, basal to plant type III polyketide synthases in phylogenetic trees, is a very long chain 2'-oxoalkylresorcinol synthase. J Biol Chem 2012; 288:2767-77. [PMID: 23223578 DOI: 10.1074/jbc.m112.430686] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The plant type III polyketide synthases (PKSs), which produce diverse secondary metabolites with different biological activities, have successfully co-evolved with land plants. To gain insight into the roles that ancestral type III PKSs played during the early evolution of land plants, we cloned and characterized PpORS from the moss Physcomitrella. PpORS has been proposed to closely resemble the most recent common ancestor of the plant type III PKSs. PpORS condenses a very long chain fatty acyl-CoA with four molecules of malonyl-CoA and catalyzes decarboxylative aldol cyclization to yield the pentaketide 2'-oxoalkylresorcinol. Therefore, PpORS is a 2'-oxoalkylresorcinol synthase. Structure modeling and sequence alignments identified a unique set of amino acid residues (Gln(218), Val(277), and Ala(286)) at the putative PpORS active site. Substitution of the Ala(286) to Phe apparently constricted the active site cavity, and the A286F mutant instead produced triketide alkylpyrones from fatty acyl-CoA substrates with shorter chain lengths. Phylogenetic analysis and comparison of the active sites of PpORS and alkylresorcinol synthases from sorghum and rice suggested that the gramineous enzymes evolved independently from PpORS to have similar functions but with distinct active site architecture. Microarray analysis revealed that PpORS is exclusively expressed in nonprotonemal moss cells. The in planta function of PpORS, therefore, is probably related to a nonprotonemal structure, such as the cuticle.
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Affiliation(s)
- Sun Young Kim
- Department of Chemistry and Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
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