Antimicrobial peptides (AMPs) kill bacteria by targeting their membranes through various mechanisms involving peptide assembly, often coupled with disorder-to-order structural transition. However, for several AMPs, similar conformational changes in cases in which small organic compounds of both endogenous and exogenous origin have induced folded peptide conformations have recently been reported. Thus, the function of AMPs and of natural host defence peptides can be significantly affected by the local complex molecular environment in vivo; nonetheless, this area is hardly explored. To address the relevance of such interactions with regard to structure and function, we have tested the effects of the therapeutic drug suramin on the membrane activity and antibacterial efficiency of CM15, a potent hybrid AMP. The results provided insight into a dynamic system in which peptide interaction with lipid bilayers is interfered with by the competitive binding of CM15 to suramin, resulting in an equilibrium dependent on peptide-to-drug ratio and vesicle surface charge. In vitro bacterial tests showed that when CM15⋅suramin complex formation dominates over membrane binding, antimicrobial activity is abolished. On the basis of this case study, it is proposed that small-molecule secondary structure regulators can modify AMP function and that this should be considered and could potentially be exploited in future development of AMP-based antimicrobial agents.
Bibliographical noteFunding Information:
This work was supported through grants provided by the Momentum Program (LP2016-2), the National Competitiveness and Excellence Program (NVKP_16-1-2016-0007) and GINOP (BIONA-NO_GINOP-2.3.2-15-2016-00017). We also thank the National Research Development and Innovation Office, Hungary (grants OTKA 104275, 115431, 124077) and additionally are grateful for grants (VEKOP-2.3.3-15-2017-00020, VEKOP-2.3.2-16-2017-00014) from the European Union and the State of Hungary, co-financed by the European Regional Development Fund. K.H. was supported by the J#nos Bolyai Research Scholarship of the Hungarian Academy of Sciences. Sz.B. thanks the ELTE Institutional Excellence Program (783-3/2018/FEKUTSRAT) supported by the Hungarian Ministry of Human Capacities.
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- IR spectroscopy
- antimicrobial peptides
- circular dichroism