Evaluation of the Effect of Less Negatively Charged Amino Acid Substitution in Synthetic Tetramer Peptide S3 Derived from Horseshoe Crab Ambocyte on its Antibacterial Properties

Introduction: The study of the effects of synthetic peptides with antibacterial properties can provide more effective antibiotics. This study designed, expressed, and investigated the Sushi 3 tetramer peptide. Subsequently, it was compared in terms of changing antibacterial properties with another Sushi3 tetramer peptide the aspartic acid and proline amino acids of which were replaced with glycine and serine amino acids. Material & Methods: First, the mentioned Sushi3 tetramer peptide sequences were designed, constructed, and named Mer1 and Mer 2, respectively, and cloned separately into plasmid pET-26b (+) and finally transferred to E.coli BL21 host (DE3). After the expression of the peptides, the presence of peptides was confirmed by SDS-PAGE and Western blotting. Afterward, the antimicrobial activity of Mer1 and Mer 2 was evaluated and compared. Finally, the toxicity of the two tetramers made on the MDA-MB-231 cell line was evaluated and compared. Findings: Mer1 and Mer 2 had similar protein expression, and the toxic effect of both peptides on the cell line was not significantly different. however, Mer 2 had more effective antimicrobial effects than Mer1 at the same concentrations. Discussion & Conclusion: Evaluation of the effect of amino acid replacement with less negatively charge on increasing the antimicrobial activity of peptides is a suitable strategy. The above results increase the possibility of designing and producing antimicrobial peptides against antibiotic-resistant strains as the next generation of antibiotics.