BIOPHYSICAL CHARACTERIZATION OF THE PEPTIDE LyeTx I AND ITS REDUCED VERSION LyeTx I mnΔK(N)

Antimicrobial peptide LyeTx I, isolated from the venom of the spider Lycosa erythrognatha (commonly known as the wolf spider), is composed of 24 amino acid residues with broad antimicrobial spectrum. Its physicochemical properties include a positive charge, which drives electrostatic interactions with negatively charged microbial membranes and allows insertion into lipid bilayers, essential for its antimicrobial efficacy. Our research group developed a shortened form composed by 14 amino acid residues, named LyeTx I mnΔK(N), which demonstrated improved antimicrobial activity and selectivity, especially against drug-resistant bacteria such as MRSA (methicillin-resistant Staphylococcus aureus) and CRAB (carbapenem-resistant Acinetobacter baumannii). This study evaluated the effect of the LyeTx I mnΔK(N) in membrane mimetic environments using 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG). Biophysical techniques zeta potential, dynamic light scattering (DLS) and isothermal titration calorimetry (ITC) were employed. The zeta potential measured the electrophoretic mobility of large unilamellar vesicles (LUVs) in the presence of the peptide, while DLS evaluated changes in the hydrodynamic diameter of the vesicles, and ITC provided thermodynamic parameters of the interaction, such as enthalpy, entropy, and binding constant. The comparison between the minimized derivative LyeTx I mnDK(N) and the native LyeTx I revealed similar effect of the peptides, but increasing both zeta potential and hydrodynamic diameters of LUVs. However, while LyeTx I showed neutralization of the negative charged vesicles, LyeTx I mnΔK(N) showed constant interactions starting. Isothermal titration calorimetry (ITC) indicated higher apparent constant of peptide-membrane interaction for the shortened version in comparision with the wide-type. Therefore, the structural modification in the LyeTx I peptide did not substantially alter its biophysical properties.