Effects of CGA-N12 on the membrane structure of Candida tropicalis cells

The antimicrobial peptide CGA-N12 (NH₂-ALQGAKERAHQQ-COOH) is an active peptide derived from chromogranin A (CGA) and consists of the 65th to 76th amino acids of the N-terminus. The results of our previous studies showed that CGA-N12 exerts anti-Candida activity by inducing apoptosis without destroying the integrity of cell membranes. In this study, the effect of CGA-N12 on the cell membrane structure of Candida tropicalis was investigated. CGA-N12 resulted in the dissipation of the membrane potential, the increase in membrane fluidity, and the outflow of potassium ions in C. tropicalis without significantly changing the ergosterol level. Fluorescence quenching was applied to evaluate the membrane channel characteristics induced by CGA-N12 through detection of the following: membrane permeability of hydrated Cl⁻ (ϕ ≈ 0.66 nm) using the membrane-impermeable halogen anion-selective fluorescent dye lucigenin, passage of the membrane-impermeable dye carboxyfluorescein (CF) (ϕ ≈ 1 nm) through the membrane, and membrane permeation of H₃O⁺ based on the membrane non-permeable pH-sensitive fluorescent dye 8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt (HPTS). In conclusion, CGA-N12 can induce the formation of non-selective ion channels <1 nm in diameter in the membranes of C. tropicalis, resulting in the leakage of potassium ions, chloride ions, and protons, among others, leading to dissipation of the membrane potential. As a result, the fluidity of membranes is increased without destroying the synthesis of ergosterol is not affected.