Branched chain lipid metabolism as a determinant of the N-acyl variation of Streptomyces natural products

Authors: Price, Neil; Jackson, Michael - Mike; Hartman, Trina; BRANDEN, GISELA - University Of Gothenburg; EK, MARGARETA - Astrazeneca Research & Development; KOCH, AARON - Cayman Chemicals; KENNEDY, PAUL - Cayman Chemicals

Submitted to: ACS Chemical Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2020
Publication Date: 1/7/2021
Citation: Price, N.P., Jackson, M.A., Hartman, T.M., Branden, G., Ek, M., Koch, A., Kennedy, P.D. 2021. Branched chain lipid metabolism as a determinant of the N-acyl variation of Streptomyces natural products. ACS Chemical Biology. 16(1):116-124. https://doi.org/10.1021/acschembio.0c00799.
DOI: https://doi.org/10.1021/acschembio.0c00799

Interpretive Summary: Tunicamycins (TUN) are natural products made by soil bacteria that greatly improve the antibiotic activity of penicillins. This could be used to overcome penicillin resistance, except for the problem that native TUN are toxic to animals. To overcome this problem we have previously made TUN derivatives that are much less toxic to animals, but are still excellent penicillin activators. In this work we have developed a new family of TUN derivatives that are even less toxic to animals, and therefore they have greater potential to improve the antibacterial activity of penicillins for uses in medicine and agriculture. This technology will allow stakeholders to potentially reduce the use of traditional antibiotics to treat livestock, which will delay antibiotic resistance, and reinstitute the use of previously shelved antibiotics that had been rendered ineffective due to antimicrobial resistance.

Technical Abstract: Branched-chain fatty acids (BCFA) are encountered in Gram-positive bacteria, but less so in other organisms. The bacterial BCFA in membranes are typically saturated, with both odd- and even-numbered carbon chain length, and with methyl-branches at either the '-1 (iso) or '-2 (anteiso) positions. The acylation with BCFA also contributes to the structural diversity of microbial natural products, and potentially modulates biological activity. For the tunicamycin (TUN) family of natural products the toxicity towards eukaryotes is highly dependent upon N-acylation with trans-2,3-unsaturated BCFA. The loss of the 2,3-unsaturation gives modified TUN with reduced eukaryotic toxicity, but crucially with retention of the synergistic enhancement of the ß-lactam group of antibiotics. Here we infer from genomics, mass spectrometry, and deuterium labeling that the trans-2,3-unsaturated TUN variants and the saturated cellular lipids found in TUN-producing Streptomyces are derived from the same pool of BCFA metabolites. Moreover, non-natural primers of BCFA metabolism are selectively incorporated into the cellular lipids of TUN-producing Streptomyces and concomitantly produce structurally novel neo-branched TUN N-acyl variants.