Genomic and Spectroscopic Signature-Based Discovery of Natural Macrolactams

Yern Hyerk Shin, Ji Hyeon Im, Ilnam Kang, Eunji Kim, Sung Chul Jang, Eunji Cho, Daniel Shin, Sunghoon Hwang, Young Eun Du, Thanh Hau Huynh, Keebeom Ko, Yoon Joo Ko, Sang Jip Nam, Takayoshi Awakawa, Jeeyeon Lee, Suckchang Hong, Ikuro Abe, Bradley S. Moore, William Fenical, Yeo Joon YoonJang Cheon Cho, Sang Kook Lee, Ki Bong Oh, Dong Chan Oh

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

The logical and effective discovery of macrolactams, structurally unique natural molecules with diverse biological activities, has been limited by a lack of targeted search methods. Herein, a targeted discovery method for natural macrolactams was devised by coupling genomic signature-based PCR screening of a bacterial DNA library with spectroscopic signature-based early identification of macrolactams. DNA library screening facilitated the efficient selection of 43 potential macrolactam-producing strains (3.6% of 1,188 strains screened). The PCR amplicons of the amine-deprotecting enzyme-coding genes were analyzed to predict the macrolactam type (α-methyl, α-alkyl, or β-methyl) produced by the hit strains. 1H-15N HSQC-TOCSY NMR analysis of 15N-labeled culture extracts enabled macrolactam detection and structural type assignment without any purification steps. This method identified a high-titer Micromonospora strain producing salinilactam (1), a previously reported α-methyl macrolactam, and two Streptomyces strains producing new α-alkyl and β-methyl macrolactams. Subsequent purification and spectroscopic analysis led to the structural revision of 1 and the discovery of muanlactam (2), an α-alkyl macrolactam with diene amide and tetraene chromophores, and concolactam (3), a β-methyl macrolactam with a [16,6,6]-tricyclic skeleton. Detailed genomic analysis of the strains producing 1-3 identified putative biosynthetic gene clusters and pathways. Compound 2 displayed significant cytotoxicity against various cancer cell lines (IC50 = 1.58 μM against HCT116), whereas 3 showed inhibitory activity against Staphylococcus aureus sortase A. This genomic and spectroscopic signature-based method provides an efficient search strategy for new natural macrolactams and will be generally applicable for the discovery of nitrogen-bearing natural products.

Original languageEnglish
Pages (from-to)1886-1896
Number of pages11
JournalJournal of the American Chemical Society
Volume145
Issue number3
DOIs
StatePublished - 25 Jan 2023

Bibliographical note

Funding Information:
This work was supported by the National Research Foundation of Korea grants funded by the Republic of Korean Government (Ministry of Science and ICT) (2020R1A2C2003518 and 2021R1A4A2001251).

Publisher Copyright:
© 2023 American Chemical Society.

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