An Smp43-Derived Short-Chain α-Helical Peptide Displays a Unique Sequence and Possesses Antimicrobial Activity against Both Gram-Positive and Gram-Negative Bacteria

Abstract

Scorpion venoms are rich resources of antimicrobial peptides (AMPs). While the short-chain noncysteine-containing AMPs have attracted much attention as templates for drug development, the antimicrobial potential of long-chain noncysteine-containing AMPs has been largely overlooked. Here, by using the online HeliQuest server, we designed and analyzed a series of 14-residue fragments of Smp43, a 43-residue long-chain noncysteine-containing AMP identified from the venom of Scorpio maurus palmatus. We found that Smp43(1-14) shows high antimicrobial activity against both Gram-positive and Gram-negative bacteria and is nontoxic to mammalian cells at the antimicrobial dosage. Sequence alignments showed that the designed Smp43(1-14) displays a unique primary structure that is different from other natural short-chain noncysteine-containing AMPs from scorpions, such as Uy17, Uy192 and IsCT. Moreover, the peptide Smp43(1-14) caused concentration-dependent fluorescence increases in the bacteria for all of the tested dyes, propidium iodide, SYTOXTM Green and DiSC3-5, suggesting that the peptide may kill the bacteria through the formation of pore structures in the plasma membrane. Taken together, our work sheds light on a new avenue for the design of novel short-chain noncysteine-containing AMPs and provides a good peptide template with a unique sequence for the development of novel drugs for use against bacterial infectious diseases.

Fine-Tuning of Alkaline Residues on the Hydrophilic Face Provides a Non-toxic Cationic α-Helical Antimicrobial Peptide Against Antibiotic-Resistant ESKAPE Pathogens

“…Membrane permeabilization caused by the peptide was determined by propidium iodide (PI, Thermo Fisher) uptake assays as described previously (Luo et al, 2021). Briefly, mid-log phase bacteria S. aureus ATCC29213 was collected by centrifugation (6,000 × g, 4 • C) and washed three times with phosphate-buffered saline (PBS).…”

“…To determine whether BmKn2-7K can induce pore structure formation in the plasma membrane, PI uptake kinetics were determined. PI is a nucleic acid binding probe that can only permeate damaged plasma membrane, thus this probe was commonly used to evaluate the pore formation ability of AMPs (Mishra et al, 2019;Luo et al, 2021). As shown in Figure 4C, rapid and dose-dependent increases of PI fluorescence were observed upon the addition of BmKn2-7K, indicating that peptide treatment induced the formation of pore structures in the bacterial membrane.…”

“…In recent studies, many attempts have been made to improve the performance of CαAMPs. These strategies involve re-engineering natural CαAMP sequences by site-directed mutation (Ahmad et al, 2009;Irazazabal et al, 2016;Li et al, 2016;Jiang et al, 2020), fragmentation (Luo et al, 2021) or chemical modification (Zarina and Nanda, 2014;Nayak et al, 2018;Mourtada et al, 2019;Mwangi et al, 2019;Li et al, 2020), computational approaches based on natural templates and statistical analysis (Loose et al, 2006;Nagarajan et al, 2018Nagarajan et al, , 2019, or designing de novo sequences by using simple alkaline vs hydrophobic amino acid combinations (Deslouches et al, 2005(Deslouches et al, , 2013Hu et al, 2011;Lakshmaiah Narayana et al, 2020). However, partly due to the complexity of the structure-activity relationships, which are derived from the sequence diversity of the peptides, progress in CαAMP optimization is still very limited and few CαAMPs have successfully achieved FDA approval (Greber and Dawgul, 2017;Ghosh et al, 2019;Torres et al, 2019).…”

The Potent Antitumor Activity of Smp43 against Non-Small-Cell Lung Cancer A549 Cells via Inducing Membranolysis and Mitochondrial Dysfunction

“…Therefore, designing novel peptide derivatives with fewer residues and improved activity has become an interesting research field. Smp43(1–14) is a unique fragment among a series of 14-residue fragments of Smp43 that exerts enhanced antimicrobial activity compared to its parent peptide by integrating into the plasma membrane of bacteria and inducing the formation of pores [ 46 ]. Further, CD spectra analysis and Psipred prediction suggest that Smp43(1–14) adopts a helical structure [ 47 ].…”