In our previous published article (https://doi.org/10.1007/s10989-019-09883-7), caP4—a cationic peptide of 2.97 kDa from Curcuma pseudomontana L. (Zingiberaceae) with sequences ASSCKPS and ASSKWVAPSEW showed significant antibacterial activity against Escherichia coli and Staphylococcus aureus. In the present study, circular dichroism (CD) data of caP4 showed 0% α-helix, 21.6% β-sheet, 31.2% β-turns, and 47.2% random coils. Further, the study was focused on understanding the mode of action of caP4 against E. coli. At 8 µg/ml (MIC), caP4 permeabilized the cell membrane with maximum recorded at 50 min. Scanning electron microscopy analysis of E. coli cells with caP4 at 16 µg/ml showed disorientation of the membrane surface. Cetyl pyridinium chloride (CPC, 10 µg/ml-IC₅₀), Mitomycin C (10 µg/ml-IC₅₀), Colchicine (25 µg/ml-IC₅₀), Cytochalasin B (30 µg/ml-IC₅₀) and Cibacron blue (25 µg/ml-IC₅₀) were used as cell growth inhibitors with or without caP4 (8 µg/ml) to check the action of peptide intracellularly. E. coli cells with caP4 showed 100% cell death at 100 min. E. coli cells pre-treated with caP4 for 30 min showed 100% and 96% cell death at 60 min and 56 min with CPC and Mitomycin C respectively, suggesting that caP4 is acting by entering into the cell membrane and thus inhibit protein synthesis similar to CPC and Mitomycin C, whereas Colchicine, Cytochalasin B, Cibacron blue did not show significant cell death with pre and post-treatment of caP4. Thus, the study showed the synergistic effect of caP4 with cell growth inhibitors CPC and Mitomycin C in enhancing the antibacterial activity. Thus the data provide a new insight to understand the mechanism of antibiotic activity of caP4 and could lay the foundation for developing plant based antibacterial drugs in future to combat drug resistant microbes.

在我们先前发表的文章（https://doi.org/10.1007/s10989-019-09883-7）中，caP4 —一种来自Curcuma pseudomontana L.（Zingiberaceae）的2.97 kDa阳离子肽，序列为ASSCKPS和ASSKWVAPSEW，显示出显着的抗菌活性抵抗大肠杆菌和金黄色葡萄球菌。在本研究中，caP4的圆二色性（CD）数据显示0％α-螺旋，21.6％β-折叠，31.2％β-转弯和47.2％随机线圈。此外，该研究集中在理解caP4对大肠杆菌的作用方式。浓度为8 µg / ml（MIC），caP4透化细胞膜，在50分钟时记录最大值。用16 µg / ml的caP4对大肠杆菌细胞进行的扫描电子显微镜分析表明，膜表面方向不正确。氯化十六烷基吡啶鎓（CPC，10 µg / ml-IC ₅₀），丝裂霉素C（10 µg / ml-IC ₅₀），秋水仙碱（25 µg / ml-IC ₅₀），细胞松弛素B（30 µg / ml-IC ₅₀）和带有或不带有caP4（8 µg / ml）的烟碱蓝（25 µg / ml-IC ₅₀）被用作细胞生长抑制剂，以检查细胞内肽的作用。具有caP4的大肠杆菌细胞在100分钟时显示100％的细胞死亡。大肠杆菌用caP4预处理30分钟的细胞在60分钟和56分钟时分别用CPC和丝裂霉素C分别显示100％和96％的细胞死亡，这表明caP4通过进入细胞膜起作用并因此抑制了蛋白质的合成，类似于CPC和丝裂霉素C，而秋水仙碱，细胞松弛素B，西巴龙蓝在caP4的治疗前后均未显示明显的细胞死亡。因此，该研究显示了caP4与细胞生长抑制剂CPC和丝裂霉素C在增强抗菌活性方面的协同作用。因此，这些数据为了解caP4抗生素活性的机制提供了新的见解。  并为将来开发基于植物的抗菌药物以对抗耐药微生物奠定基础。