Ren Wenkai/Professor Peng Yuanyi's teamwork revealed that melatonin targets type II citrate synthase to inhibit Gram-negative bacteria

Bacterial infections caused by Gram-negative pathogens pose a serious threat to public health worldwide, and with the increase in bacterial drug resistance, there is an urgent need for novel antimicrobial drugs against bacterial infections
.

But few compounds are currently approved in clinical settings, and repurposing compounds for other uses offers a fruitful strategy for developing new antibiotics
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Recently, Professor Ren Wenkai's research group from South China Agricultural University, Professor Peng Yuanyi's research group from Southwest University and Professor Liu Yuan's research group from Yangzhou University School of Veterinary Medicine jointly published a research titled "Melatonin inhibits Gram-negative pathogens by targeting citrate synthase" in Science China Life Sciences The paper reveals the antibacterial target and mechanism of melatonin-specific inhibition of Gram-negative bacteria
.

In this study, animal experiments found that melatonin can effectively prevent and treat infections caused by bovine-derived Pasteurella multocida (P.
multocida) (significantly improve mouse survival and reduce lung bacterial colonization)
.

Transcriptomic analysis showed that the differential genes were mainly enriched in membrane function, bacterial metabolism and other pathways; membrane permeability, fluorescence staining, scanning and transmission electron microscopy experiments showed that melatonin can destroy the integrity of bacterial cell membranes
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Metabolomics analysis showed that the differential metabolites were mainly enriched in the TCA cycle and other pathways.
Further exploration found that melatonin significantly inhibited the activity of bacterial citrate synthase, while exogenous citric acid could significantly antagonize the bacteriostatic effect of melatonin.
The citrate synthase (gltA) gene deletion strain and the complementing strain were constructed, indicating that melatonin plays an antibacterial effect by inhibiting the activity of citrate synthase to reduce the synthesis of citrate
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Citrate synthase purified by prokaryotic expression combined with surface plasmon resonance analysis (LSPR) showed that melatonin has high affinity (binding energy: 7.
62e-5 M) for type II citrate synthase (derived from Gram-negative bacteria), It has a lower binding capacity to type I citrate synthase (mainly found in Gram-positive bacteria and eukaryotes)
.

Homology modeling and molecular docking analysis revealed that melatonin can form hydrophobic interactions with N361, L301, M302, and H265 of type II citrate synthase, and form hydrogen bonds with D363, R300, P263, and R307 (R300 > D363 > H265 )
.

LSPR analysis found that the affinity of melatonin to citrate synthase mutants CS (R300A, D363A, H265A), CS (R300A, D363A) and CS (R300A) was significantly reduced, 2.
83e-4, 2.
65e-4 and 1.
83e-4M, indicating that melatonin inhibits its function by binding to the R300, D363, and H265 sites of type II citrate synthase
.

This study provides new targets and research ideas for the development of new antibacterial drugs
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Melatonin targets gram-negative bacteria type II citrate synthase.
He Fang, a doctoral student at the School of Veterinary Medicine, Southwest University, and Professor Liu Yuan, School of Veterinary Medicine, Yangzhou University are the co-first authors of the article.
Professor Ren Wenkai, School of Animal Science, South China Agricultural University, Southwest University Professor Peng Yuanyi and Associate Professor Li Nengzhang of the University of Veterinary Medicine are the corresponding authors
.

For research details, please read the original text▼[Click the link below or read the original text]He, F.
, Liu, Y.
, Li, P.
, Wu, X.
, Xia, Y.
, Zhang, D.
, Li, N.
, Peng , Y.
, Zhu, G.
, Hardeland, R.
, et al.
(2022).
Melatonin inhibits Gram-negative pathogens by targeting citrate synthase.
Sci China Life Sci 65, https://doi.
org/10.
1007/s11427- 021-2032-9