Mularski Anna, Wilksch Jonathan J, Hanssen Eric, Strugnell Richard A, Separovic Frances
School of Chemistry, The University of Melbourne, VIC 3010, Australia.
Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, The University of Melbourne, VIC 3010, Australia.
Biochim Biophys Acta. 2016 Jun;1858(6):1091-8. doi: 10.1016/j.bbamem.2016.03.002. Epub 2016 Mar 4.
Time-resolved AFM images revealed that the antimicrobial peptide (AMP) caerin 1.1 caused localised defects in the cell walls of lysed Klebsiella pneumoniae cells, corroborating a pore-forming mechanism of action. The defects continued to grow during the AFM experiment, in corroboration with large holes that were visualised by scanning electron microscopy. Defects in cytoplasmic membranes were visualised by cryo-EM using the same peptide concentration as in the AFM experiments. At three times the minimum inhibitory concentration of caerin, 'pores' were apparent in the outer membrane. The capsule of K. pneumoniae AJ218 was unchanged by exposure to caerin, indicating that the ionic interaction of the positively charged peptide with the negatively charged capsular polysaccharide is not a critical component of AMP interaction with K. pneumoniae AJ218 cells. Further, the presence of a capsule confers no advantage to wild-type over capsule-deficient cells when exposed to the AMP caerin.
时间分辨原子力显微镜图像显示，抗菌肽（AMP）caerin 1.1在裂解的肺炎克雷伯菌细胞壁上造成局部缺陷，证实了其成孔作用机制。在原子力显微镜实验过程中，这些缺陷持续扩大，这与扫描电子显微镜观察到的大洞相一致。使用与原子力显微镜实验相同的肽浓度，通过冷冻电镜观察到细胞质膜中的缺陷。在caerin最小抑菌浓度的三倍时，外膜中出现了“孔”。肺炎克雷伯菌AJ218的荚膜在暴露于caerin后未发生变化，这表明带正电荷的肽与带负电荷的荚膜多糖之间的离子相互作用不是AMP与肺炎克雷伯菌AJ218细胞相互作用的关键组成部分。此外，当暴露于AMP caerin时，野生型细胞与缺乏荚膜的细胞相比，荚膜的存在并没有优势。
