Antimicrobial peptides (AMPs) represent a large and ubiquitous group of peptides. The current crisis in antibiotic
therapy has led to an intensified search for new antimicrobial agents. In this regard, scorpion venom constitutes a rich
source of biologically active peptides including AMPs. In the present study, the purification of a novel peptide with antimicrobial
activity against the Gram-negative bacteria Klebsiella pneumoniae is described. This antimicrobial peptide,
named Cm38, was purified from Centruroides margaritatus scorpion venom using a two-step chromatographic strategy
using C8 and C18 columns. This toxin inhibits the proliferation of the Gram-negative bacteria Klebsiella pneumoniae with
a Minimal Inhibitory Concentration (MIC) of 64 μM. An analysis of the N-terminal sequence of Cm38 revealed a close
structural relationship to Cn11, a Na+-channel modulator toxin previously isolated from Centruroides noxius scorpion
venom. Therefore, to test Cm38 for effects on ion channels, we measured its effects on action potential firing in cultured
dorsal root ganglion neurons. Cm38 depolarized and increased action potential firing in a subset of neurons tested. The
present work reports a new peptide related to Cn11 with antimicrobial properties that is also active in neurons.
Keywords: Action potential firing, antimicrobial peptide, Centruroides margaritatus, Cn11, scorpion.
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