Sudheendra U S, Dhople Vishnu, Datta Aritreyee, Kar Rajiv K, Shelburne Charles E, Bhunia Anirban, Ramamoorthy Ayyalusamy
Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA; Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055, USA.
Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VII (M), Kolkata 700054, India.
Eur J Med Chem. 2015 Feb 16;91:91-9. doi: 10.1016/j.ejmech.2014.08.021. Epub 2014 Aug 7.
Human beta defensin-3 (HβD-3) is a host-defense protein exhibiting antibacterial activity towards both Gram-negative and Gram-positive bacteria. There is considerable interest in the function of this protein due to its increased salt tolerance and activity against Gram-positive Staphylococcus aureus. In this study, analogs of HβD-3 devoid of N and C terminal regions are investigated to determine the influence of specific structural motif on antimicrobial activity and selectivity between Gram-positive and Gram-negative bacteria. Circular dichroism, fluorescence and solid-state NMR experiments have been used to investigate the conformation and mode of action of HβD3 analogs with various model membranes to mimic bacterial inner and outer membranes and also mammalian membranes. Our studies specifically focused on determining four major characteristics: (i) interaction of HβD3 analogs with phospholipid vesicles composed of zwitterionic PC or anionic PE:PG vesicles and LPS; (ii) conformation of HβD3-peptide analogs in the presence of PC or PE:PG vesicles; (iii) ability of HβD3 analogs to permeate phospholipid vesicles composed of PC or PE:PG; and (iv) activities on bacteria cells and erythrocytes. Our results infer that the linear peptide L25P and its cyclic form C25P are more active than L21P and C21P analogs. However, they are less active than the parent peptide, thus pointing towards the importance of the N terminal domain in its biological activity. The variation in the activities of L21P/C21P and L25P/C25P also suggest the importance of the positively charged residues at the C terminus in providing selectivity particularly to Gram-negative bacteria.
人β-防御素-3（HβD-3）是一种宿主防御蛋白，对革兰氏阴性菌和革兰氏阳性菌均具有抗菌活性。由于其增强的耐盐性以及对革兰氏阳性金黄色葡萄球菌的活性，人们对该蛋白的功能有着浓厚的兴趣。在本研究中，对缺失N端和C端区域的HβD-3类似物进行了研究，以确定特定结构基序对抗菌活性以及革兰氏阳性菌和革兰氏阴性菌之间选择性的影响。利用圆二色性、荧光和固态核磁共振实验，研究了HβD3类似物与各种模型膜的构象和作用模式，这些模型膜可模拟细菌内膜和外膜以及哺乳动物膜。我们的研究特别聚焦于确定四个主要特征：（i）HβD3类似物与由两性离子PC或阴离子PE:PG囊泡及LPS组成的磷脂囊泡的相互作用；（ii）在PC或PE:PG囊泡存在下HβD3肽类似物的构象；（iii）HβD3类似物渗透由PC或PE:PG组成的磷脂囊泡的能力；（iv）对细菌细胞和红细胞的活性。我们的结果表明，线性肽L25P及其环状形式C25P比L21P和C21P类似物更具活性。然而，它们的活性低于亲本肽，这表明N端结构域在其生物活性中的重要性。L21P/C21P和L25P/C25P活性的差异也表明C端带正电荷的残基在提供选择性方面的重要性，特别是对革兰氏阴性菌的选择性。
