Effects of rhodomyrtone on Gram-positive bacterial tubulin homologue FtsZ.
Rhodomyrtone, a natural antimicrobial compound, displays potent activity against many Gram-positive pathogenic bacteria, comparable to last-defence antibiotics including vancomycin and daptomycin. Our previous studies pointed towards effects of rhodomyrtone on the bacterial membrane and cell wall. In addition, a recent molecular docking study suggested that the compound could competitively bind to the main bacterial cell division protein FtsZ. In this study, we applied a computational approach (in silico),in vitro, andin vivoexperiments to investigate molecular interactions of rhodomyrtone with FtsZ. Using molecular simulation, FtsZ conformational changes were observed in both (S)- and (R)-rhodomyrtone binding states, compared with the three natural states of FtsZ (ligand-free, GDP-, and GTP-binding states). Calculations of free binding energy showed a higher affinity of FtsZ to (S)-rhodomyrtone (-35.92 ± 0.36 kcal mol-1) than the GDP substrate (-23.47 ± 0.25 kcal mol-1) while less affinity was observed in the case of (R)-rhodomyrtone (-18.11 ± 0.11 kcal mol-1).In vitroexperiments further revealed that rhodomyrtone reduced FtsZ polymerization by 36% and inhibited GTPase activity by up to 45%. However, the compound had no effect on FtsZ localization inBacillus subtilisat inhibitory concentrations and cells also did not elongate after treatment. Higher concentrations of rhodomyrtone did affect localization of FtsZ and also affected localization of its membrane anchor proteins FtsA and SepF, showing that the compound did not specifically inhibit FtsZ but rather impaired multiple divisome proteins. Furthermore, a number of cells adopted a bean-like shape suggesting that rhodomyrtone possibly possesses further targets involved in cell envelope synthesis and/or maintenance.
Excellence Research Laboratory on Natural Products, Faculty of Science and Natural Product Research Center of Excellence, Prince of Songkla University, Hat Yai, Thailand; Department of Microbiology, Faculty of Science, Prince of Songkla University, Hat Yai, Thailand.
Dennapa
D
Saeloh
Bacterial Cell Biology, Swammerdam Institute for Life Sciences, University of Amsterdam , Amsterdam , Netherlands.
Michaela
M
Wenzel
Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand; Center of Innovative Nanotechnology, Chulalongkorn University, Bongkok, Thailand.
Thanyada
T
Rungrotmongkol
Bacterial Cell Biology, Swammerdam Institute for Life Sciences, University of Amsterdam , Amsterdam , Netherlands.
Leendert Willem
LW
Hamoen
Excellence Research Laboratory on Natural Products, Faculty of Science and Natural Product Research Center of Excellence, Prince of Songkla University, Hat Yai, Thailand; Department of Biomedical Science, Faculty of Medicine, Prince of Songkla University, Hat Yai, Thailand.
Varomyalin
V
Tipmanee
Excellence Research Laboratory on Natural Products, Faculty of Science and Natural Product Research Center of Excellence, Prince of Songkla University, Hat Yai, Thailand; Department of Microbiology, Faculty of Science, Prince of Songkla University, Hat Yai, Thailand.
Supayang Piyawan
SP
Voravuthikunchai
Binding free energy; Cell division; Molecular dynamics simulation; Rhodomyrtone; Tubulin homologue FtsZ