Effects of Dimerization on the Structure and Biological Activity of Antimicrobial Peptide Ctx-Ha

Abstract

It is well known that cationic antimicrobial peptides (cAMPs) are potential microbicidal agents for the increasing problem of antimicrobial resistance. However, the physicochemical properties of each peptide need to be optimized for clinical use. To evaluate the effects of dimerization on the structure and biological activity of the antimicrobial peptide Ctx-Ha, we have synthesized the monomeric and three dimeric (Lys-branched) forms of the Ctx-Ha peptide by solid-phase peptide synthesis using a combination of 9-fluorenylmethyloxycarbonyl (Fmoc) and t-butoxycarbonyl (Boc) chemical approaches. The antimicrobial activity assay showed that dimerization decreases the ability of the peptide to inhibit growth of bacteria or fungi; however, the dimeric analogs displayed a higher level of bactericidal activity. In addition, a dramatic increase (50 times) in hemolytic activity was achieved with these analogs. Permeabilization studies showed that the rate of carboxyfluorescein release was higher for the dimeric peptides than for the monomeric peptide, especially in vesicles that contained sphingomyelin. Despite different biological activities, the secondary structure and pore diameter were not significantly altered by dimerization. In contrast to the case for other dimeric cAMPs, we have shown that dimerization selectively decreases the antimicrobial activity of this peptide and increases the hemolytic activity. The results also show that the interaction between dimeric peptides and the cell wall could be responsible for the decrease of the antimicrobial activity of these peptides.

Multivalent display of the antimicrobial peptides BP100 and BP143

“…In contrast, despite the fact that a significant decrease of the MIC values was not observed, the preassembly of multiple copies of BP100 and BP143 did have an important effect on the bactericidal activity. The results showed that the carbopeptides 1 – 3 were significantly more potent than the corresponding monomers, which is in agreement with previous studies [34–35]. This ability to kill the bacteria rapidly confers them a greater capacity to control bacterial cell growth, which may be important for their future potential use as bactericidal agents.…”

Melittin peptides exhibit different activity on different cells and model membranes

“…Similarly, great differences are seen between the native and P14C peptides although they have the same charge and hydrophobicity. The effects of dimerization of AMP, CtxHa, have recently been reported (Lorenzon et al 2012). The difference in the biological activity of the monomer and dimeric peptide could not be explained by different mechanisms of action, secondary structure or proximity of the peptide chains and may be sequence dependent.…”

“…Although the mechanism of AMP action is unknown and pore formation in cell membranes may be responsible for lytic ability, it is well established that AMP interact directly with the cell membrane surface and are able to enter the lipid bilayer, resulting in cell membrane disruption and leakage of cytoplasmic components which leads to killing of microbes (Lee et al 2010;Izadpanah and Gallo 2005;Lorenzon et al 2012;Sani et al 2013). AMP have attracted much attention as an alternative to antibiotics because of their effect against bacterial infections and drug resistant bacteria (Juba et al 2013;AnayaLopez et al 2013).…”

Structure and membrane interactions of the homodimeric antibiotic peptide homotarsinin

“…This sequence shows a significant increase in antimicrobial activity when the two chains are linked by a central disulfide bond19. In contrast, the ability of another peptide Ctx-Ha to inhibit the growth of microorganisms is reduced upon dimerization while its hemolytic activity increased20.…”