Myotoxin-4 or Crotamine-4. Specifically modifies voltage-sensitive Na⁺channels, inhibits K⁺ channels and exhibits analgesic effects. This snake myotoxin family member is a cationic peptide with multiple functions. It acts as a cell-penetrating peptide (CPP), and has antimicrobial activities, hind limb paralysis, and severe muscle necrosis by a non-enzymatic mechanism. As a cell-penetrating peptide, crotamine has high specificity for actively proliferating cells, and interacts inside the cell with subcellular and subnuclear structures, like vesicular compartments, chromosomes and centrioles (Hayashi et al. 2008). The toxin  selectively inhibits Kv1.1/KCNA1, Kv1.2/KCNA2 and Kv1.3/KCNA3 channels with IC₅₀ values of 369, 386 and 287 nM, respectively (Peigneur et al. 2012). As an antimicrobial peptide, crotamine shows antibacterial activity against E. coli and B. subtilis, and antifungal activity against Candida spp., Trichosporon spp. and C. neoformans. It kills bacteria through membrane permeabilization (Kerkis et al. 2004).