<abstract xmlns="http://www.w3.org/1999/xhtml"><p>C-terminal amidation is a common feature of wild type membrane disrupting antimicrobial peptides (AMPs). Empirical evidence suggests that this modification increases antimicrobial efficacy. However, the actual role of C-terminal amidation in the molecular mechanism of action of AMPs is not fully understood. Amidation alters two key properties simultaneously: the net charge and helicity of the peptide, both of which are implicated in the mechanism of action. However, the differences between the physicochemical properties of the carboxyl and amide moieties have been disregarded in former studies. In this study we assessed whether the difference in activity is only caused by changes in the helicity and overall charge of a peptide, i.e. whether the chemistry of the terminus is otherwise irrelevant. To do so, the membrane disrupting activity of a modified aurein 1.2 peptide was studied in which a secondary amide was formed with a terminal methyl group, instead of the primary amide as in the wild type peptide. Results of quartz crystal microbalance, dye leakage and circular dichroism experiments show that the activity of the modified peptide is substantially reduced compared to the wild type peptide, in particular that the modified peptide exhibited a much-reduced ability to bind to the membrane. Thus, the primary amide at the C-terminus is required to bind to the membrane, and a secondary amide cannot serve the same purpose. We hypothesize that this difference is related to the hydration state of the terminus. The lack of membrane binding ability of the modified peptide identifies the primary amide moiety at the C terminus as a specific membrane binding motif.</p></abstract>

C-terminal amidation is a common feature of wild type membrane disrupting antimicrobial peptides (AMPs). Empirical evidence suggests that this modification increases antimicrobial efficacy. However, the actual role of C-terminal amidation in the molecular mechanism of action of AMPs is not fully understood. Amidation alters two key properties simultaneously: the net charge and helicity of the peptide, both of which are implicated in the mechanism of action. However, the differences between the physicochemical properties of the carboxyl and amide moieties have been disregarded in former studies. In this study we assessed whether the difference in activity is only caused by changes in the helicity and overall charge of a peptide, i.e. whether the chemistry of the terminus is otherwise irrelevant. To do so, the membrane disrupting activity of a modified aurein 1.2 peptide was studied in which a secondary amide was formed with a terminal methyl group, instead of the primary amide as in the wild type peptide. Results of quartz crystal microbalance, dye leakage and circular dichroism experiments show that the activity of the modified peptide is substantially reduced compared to the wild type peptide, in particular that the modified peptide exhibited a much-reduced ability to bind to the membrane. Thus, the primary amide at the C-terminus is required to bind to the membrane, and a secondary amide cannot serve the same purpose. We hypothesize that this difference is related to the hydration state of the terminus. The lack of membrane binding ability of the modified peptide identifies the primary amide moiety at the C terminus as a specific membrane binding motif.

The role of C-terminal amidation in the mechanism of action of the antimicrobial peptide aurein 1.2

The EuroBiotech Journal

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

C-terminal amidation is a common feature of wild type membrane disrupting antimicrobial peptides (AMPs). Empirical evidence suggests that this modification...

Peptides	Fluorescence intensity increase (%)
Aurein 1.2 –NH₂ (wild type)	30
Aurein 1.2 –COOH	1
Aurein 1.2 –NH-CH₃	0

Medium	%Helicity
Medium	aurein1.2-NH₂	aurein1.2-NH-CH₃	aurein1.2-COOH
PBS	9	4	9
DMPC	25	5	24
DMPC:cholesterol 9:1	20	5	12
DMPC:DMPG 4:1	38	8	32

The role of C-terminal amidation in the mechanism of action of the antimicrobial peptide aurein 1.2

Article Category: Research Article

Online veröffentlicht: 18. Jan. 2020

Seitenbereich: 25 - 31

DOI: https://doi.org/10.2478/ebtj-2020-0004

Schlüsselwörter
antimicrobial peptide, membrane disruption, carpet mechanism, activity

© 2020 Mahdi Shahmiri and Adam Mechler, published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Dye leakage results with neat DMPC liposomes

Results of CD measurements

The role of C-terminal amidation in the mechanism of action of the antimicrobial peptide aurein 1.2

Article Category: Research Article

Online veröffentlicht: 18. Jan. 2020

Seitenbereich: 25 - 31

DOI: https://doi.org/10.2478/ebtj-2020-0004

Schlüsselwörterantimicrobial peptide, membrane disruption, carpet mechanism, activity

© 2020 Mahdi Shahmiri and Adam Mechler, published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Dye leakage results with neat DMPC liposomes

Results of CD measurements

Schlüsselwörter
antimicrobial peptide, membrane disruption, carpet mechanism, activity