Key Laboratory of Animal Models and Human Diseases Mechanisms, Kunming Institute of Zoology, the Chinese Academy of Sciences,Kunming Yunnan 650223, China;
2.
Cell Biology and Genetics Section of Kunming Medical College, Kunming Yunnan 650031, China;
3.
Biochemistry Section of Kunming Medical College, Kunming Yunnan 650031, China;4. Department of Urology, the First Affiliated Hospital of Kunming Medical College, Kunming Yunnan 650032, China)
4.
Department of Urology, the First Affiliated Hospital of Kunming Medical College, Kunming Yunnan 650032, China)
OH-CATH is a novel cathelicidin identified from king cobra. It showed strong antibacterial activity against various bacteria in the presence of 1% NaCl and no haemolytic activity toward human red blood cells even at a high concentration. OH-CATH might serve as model molecules for the development of antimicrobial drugs. Understanding the action mechanism of OH-CATH and the reason for its selectivity against microbes is very important for this purpose. The bactericidal effect of the king cobra antimicrobial peptide OH-CATH on Gram-negative Escherichia coli (ATCC 25922) is observed by scanning electron microscopy (SEM) and transmitted electron microscopy (TEM). The SEM and TEM results suggested that the bactericidal mechanism of OH-CATH against Escherichia coli happened in three steps. Firstly, OH-CATH attached to the negatively charged bacterial wall by positively charged amino acid residues. In the second step, the accumulated OH-CATH aggregated and damaged the bacteria membrane in a pore-forming manner. In the last step, with the damage of cell permeability, the contents of the cells were released and eventually cells died.