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

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 multifaceted nature of antimicrobial peptides: current synthetic chemistry approaches and future directions

“…In addition, amidation can alter the helicity of the AMP. 58 For the synthetic AMP modelin-5, both amidated and un-amidated analogues can bind to lipid bilayers, but upon binding, helix formation is only induced in the amidated analogue. 59 However, while amidation can improve antimicrobial activity, for some AMPs little difference is observed with or without amidation.…”

Cationic Hylin Bioactive Peptides from Boana pulchella (Anura: Hylidae): Activity, Structure, and Interaction with Lipid Membranes

“…The analysis of the primary sequences of the peptides identified from the lyophilized crude skin extract of B. pulchella by RP-HPLC followed by LC-ESI-MS/MS revealed the presence of several peptides including acidic and amidated C-terminus fragments of the mature peptides identified from mRNAs. This post-transcriptional modification occurs commonly in AMPs and is necessary for membrane binding [6].…”

Generation of truncated derivatives through in silico enzymatic digest of peptide GV30 target MRSA both in vitro and in vivo

“…Surprisingly, compared to GV30, GV23 showed faster antibacterial kinetics both in the time-killing test and the SYTOX green permeability test. A possible explanation is that the N-terminal amidation exposed an N-terminal positive charge and enhanced the structural stability of α-helix [54] , [55] . In this step, a safer derivative of GV30 was obtained while retaining antibacterial activity.…”