Li, Ruifang, et al. The Antifungal Peptide CGA-N12 Inhibits Cell Wall Synthesis of Candida Tropicalis by Interacting with KRE9. Biochemical Journal, 2020, doi:10.1042/bcj20190678
Abstract
CGA -N12, an antifungal peptide derived from chromogranin A, has specific antagonistic activity against Candida spp., especially against Candida tropicalis, by inducing cell apoptosis. However, the effect of CGA -N12 on the Candida cell wall is unknown. The Candida protein KRE9, which possesses β -1,6 -glucanase activity, was screened by affinity chromatography after binding to CGA -N12. In this study, the effect of CGA -N12 on KRE9 and the interaction between CGA -N12 and KRE9 was studied to clarify the effect of CGA -N12 on C. tropicalis cell wall synthesis. The effect of CGA – N12 on recombinant KRE9 β -1,6 -glucanase activity was investigated by analy zing the consumption of glucose. The results showed that CGA -N12 inhibited the activity of KRE9. After C. tropicalis was treated with CGA -N12, the structure of the C. tropicalis cell wall was damaged. The interaction between CGA -N12 and KRE9 was analy zed by isothermal titration calorimetry (ITC). The results showed that their interaction process was involved an endothermic reaction, and the interaction force was mainly hydrophobic with a few electrostatic forces. The results of the fluorescence resonance energy transfer (FRET) assay showed that the distance between CGA -N12 and KRE9 was 7~10 nm during their interaction. Therefore, we concluded that the target of CGA – N12 in the C. tropicalis cell membrane is KRE9, and that CGA -N12 weakly binds to KRE9 within a 7~10 nm distance and inhibits KRE9 activity.