IsCT‐based analogs intending better biological activity

Abstract

IsCT1‐NH2 is a cationic antimicrobial peptide isolated from the venom of the scorpion Opisthacanthus madagascariensis that has a tendency to form an α‐helical structure and shows potent antimicrobial activity and also inopportunely shows hemolytic effects. In this study, five IsCT1 (ILGKIWEGIKSLF)‐based analogs with amino acid modifications at positions 1, 3, 5, or 8 and one analog with three simultaneous substitutions at the 1, 5, and 8 positions were designed. The net charge of each analog was between +2 and +3. The peptides obtained were characterized by mass spectrometry and analyzed by circular dichroism for their structure in different media. Studies of antimicrobial activity, hemolytic activity, and stability against proteases were also carried out.Peptides with a substitution at position 3 or 5 ([L]3‐IsCT1‐NH2, [K]3‐IsCT1‐NH2, or [F]5‐IsCT1‐NH2) showed no significant change in an activity relative to IsCT1‐NH2. The addition of a proline residue at position 8 ([P]8‐IsCT1‐NH2) reduced the hemolytic activity as well as the antimicrobial activity (MIC ranging 3.13‐50 μmol L−1), and the addition of a tryptophan residue at position 1 ([W]1‐IsCT1‐NH2) increased the hemolytic activity (MHC = 1.56 μmol L−1) without an improvement in antimicrobial activity. The analog [A]1[F]5[K]8‐IsCT1‐NH2, which carries three simultaneous modifications, presented increasing or equivalent values in antimicrobial activity (MIC approximately 0.38 and 12.5 μmol L−1) with a reduction in hemolytic activity. In addition, this analog presented the best resistance against proteases. This kind of strategy can find functional hotspots in peptide molecules in an attempt to generate novel potent peptide antibiotics.

Synthetic Peptide Derived from Scorpion Venom Displays Minimal Toxicity and Anti-infective Activity in an Animal Model

“…Based on the structure of the scorpion venom peptide IsCT1-NH 2 , we designed six synthetic derivatives using the server Heliquest . Previous work revealed that single and double amino acid substitutions in positions 3, 5, 7, 8, or 9 of the original sequence led to reduced toxicity and modulated antibacterial activity and hinted that increased net positive charge led to enhanced antimicrobial. ,,,, Here, we performed multiple amino acid modifications on the hydrophobic and hydrophilic faces of the helical structure (Figure ) based on what was learned with the preliminary single and double substitutions studies. This strategy led us to generate peptides with net positive charge values ranging from +3 to +6.…”

“…Venoms are beginning to be explored as a source of novel antibiotics. − Here, we reprogramed a linear short α-helical AMP (IsCT1-NH 2 ; ILG­KIW­EGI­KSLF-NH 2 ) derived from the venom of the Opisthacanthus madagascariensis , a scorpion endemic to the Isalo National Park in Madagascar . IsCT1-NH 2 showed potent antibacterial activity against both Gram-positive and negative bacteria with concentrations ranging from 1 to 50 μmol L –1 , , making it a good candidate for subsequent development into an antimicrobial drug.…”

“…Venoms are beginning to be explored as a source of novel antibiotics. − Here, we reprogramed a linear short α-helical AMP (IsCT1-NH 2 ; ILG­KIW­EGI­KSLF-NH 2 ) derived from the venom of the Opisthacanthus madagascariensis , a scorpion endemic to the Isalo National Park in Madagascar . IsCT1-NH 2 showed potent antibacterial activity against both Gram-positive and negative bacteria with concentrations ranging from 1 to 50 μmol L –1 , , making it a good candidate for subsequent development into an antimicrobial drug. However, its therapeutic applications have been hampered by its toxicity. − Increasing the net positive charge of peptides has been reported to successfully increase their interaction with negatively charged bacterial membranes, thus increasing their antibacterial activity to concentrations lower than those required to exert toxicity against mammalian cells .…”

“…IsCT1-NH 2 showed potent antibacterial activity against both Gram-positive and negative bacteria with concentrations ranging from 1 to 50 μmol L –1 , , making it a good candidate for subsequent development into an antimicrobial drug. However, its therapeutic applications have been hampered by its toxicity. − Increasing the net positive charge of peptides has been reported to successfully increase their interaction with negatively charged bacterial membranes, thus increasing their antibacterial activity to concentrations lower than those required to exert toxicity against mammalian cells . This strategy was successfully used, for example, to generate highly antimicrobial analogs of VmCT1, stigmurin, TsAP-1 and TsAP-2, and polybia-CP .…”

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

“…The short-chain noncysteine-containing AMP family includes a large number of peptides that consist of 13 or 14 residues, such as IsCTs [ 23 , 24 ], StCTs [ 15 , 25 ], BmKn2 [ 26 ], lausporin-1 [ 27 ], VmCTs, VsCTs [ 28 ], OcyCs [ 29 ], meucin-13 [ 30 ], Uy17, Uy192, UyCTs [ 31 , 32 ] and pantinins [ 33 ]. Owing to their small size, short-chain peptides are considered good templates for peptide-based drug design [ 26 , 34 , 35 ]. The long-chain noncysteine-containing AMPs from scorpion venoms are also an important natural peptide resource and include hadrurin [ 36 ], BmKbpp [ 37 ], opistoporins, parabutoporin [ 38 ], pandinin-1 [ 19 ], Im1 [ 39 ], vejovine [ 40 ] and Smp43 [ 41 ].…”