Singh Shalini, Kasetty Gopinath, Schmidtchen Artur, Malmsten Martin
Department of Pharmacy, Uppsala University, Uppsala, Sweden.
Biochim Biophys Acta. 2012 Sep;1818(9):2244-51. doi: 10.1016/j.bbamem.2012.03.017. Epub 2012 Apr 2.
The mechanisms underlying antimicrobial and anti-endotoxic effects were investigated for a series of structurally related peptides derived from the C-terminal region of S1 peptidases. For this purpose, results on bacterial killing were compared to those on peptide-induced liposome leakage, and to ellipsometry and dual polarization interferometry results on peptide binding to, and disordering of, supported lipid bilayers. Furthermore, the ability of these peptides to block endotoxic effects caused by bacterial lipopolysaccharide (LPS), monitored through NO production in macrophages, was compared to the binding of these peptides to LPS, and to secondary structure formation in the peptide/LPS complex. Bacteria killing, occurring through peptide-induced membrane lysis, was found to correlate with liposome rupture, and with the extent of peptide binding to the lipid membrane, no adsorption threshold for peptide insertion being observed. Membrane and LPS binding was found to depend on peptide net charge, illustrated by LPS binding increasing with increasing peptide charge, and peptides with net negative charge being unable to lyse membranes, kill bacteria, and block LPS-induced endotoxic effect. These effects were, however, also influenced by peptide hydrophobicity. LPS binding was furthermore demonstrated to be necessary, but not sufficient, for anti-endotoxic effect of these peptides. Circular dichroism spectroscopy showed that pronounced helix formation occurs in peptide/LPS complexes for all peptides displaying anti-endotoxic effect, hence potentially linked to this functionality. Similarly, ordered secondary structure formation was correlated to membrane binding, lysis, and antimicrobial activity of these peptides. Finally, preferential binding of these peptides to LPS over the lipid membrane was demonstrated.
对一系列源自S1肽酶C末端区域的结构相关肽的抗菌和抗内毒素作用机制进行了研究。为此，将细菌杀伤结果与肽诱导的脂质体泄漏结果进行了比较，并与椭圆偏振法和双偏振干涉法关于肽与支持脂质双层的结合及无序化的结果进行了比较。此外，通过巨噬细胞中一氧化氮的产生来监测这些肽阻断细菌脂多糖（LPS）引起的内毒素作用的能力，并与这些肽与LPS的结合以及肽/LPS复合物中的二级结构形成进行了比较。发现通过肽诱导的膜裂解发生的细菌杀伤与脂质体破裂以及肽与脂质膜的结合程度相关，未观察到肽插入的吸附阈值。发现膜和LPS结合取决于肽的净电荷，LPS结合随肽电荷增加而增加说明了这一点，净负电荷的肽无法裂解膜、杀死细菌和阻断LPS诱导的内毒素作用。然而，这些作用也受肽疏水性的影响。此外，已证明LPS结合对于这些肽的抗内毒素作用是必要的，但不是充分的。圆二色光谱表明，对于所有显示抗内毒素作用的肽，在肽/LPS复合物中都会发生明显的螺旋形成，因此可能与该功能相关。同样，有序二级结构的形成与这些肽的膜结合、裂解和抗菌活性相关。最后，证明了这些肽对LPS的结合优先于脂质膜。
