Structure, Dynamics, and Activity of an All-Cysteine Mutated Human β Defensin-3 Peptide Analogue
Structure, Dynamics, and Activity of an All-Cysteine Mutated Human β Defensin-3 Peptide Analogue
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DOI：
10.1021/bi900154f
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发表时间：
2009-07-07
期刊：
影响因子：
2.9
通讯作者：
Yang, Daiwen
中科院分区：
文献类型：
--
作者：
Chandrababu, Karthik Balakrishna;Ho, Bow;Yang, Daiwen
人β防御素-3（HBD-3）是一种独特的抗菌肽。为了探索HBD-3的三维结构在其活性和选择性中的重要性，我们将HBD-3的六个半胱氨酸残基全部突变为其他氨基酸，在大肠杆菌中表达突变体（命名为Def-A），并分析突变体的活性、结构和动力学。Def-A对几种细菌菌株有活性，但活性受环境离子强度的影响。当受到囊泡如POPG或胶束如SDS，Def-A是从一个随机的线圈结构改变为一个有序的螺旋形式。我们已经确定了SDS胶束中Def-A的结构，发现它被折叠成两个不同的螺旋分开的脯氨酸扭结。我们建议，长的N-末端螺旋与许多疏水残基插入胶束内，而C-末端螺旋与一个大的正电荷补丁位于胶束外，并与胶束的带电头基相互作用。该模型得到了NMR弛豫和H-D交换数据的支持。我们的研究结果表明，除了带正电荷的残基和疏水性残基的数量，这些残基在三维空间中的排列是重要的人β防御素的抗菌选择性和盐依赖性活性。
Human beta defensin-3 (HBD-3) is a unique potent antimicrobial peptide. To explore the importance of the three-dimensional structure of HBD-3 in its activity and selectivity, we have mutated all six cysteine residues of HBD-3 to other amino acids, expressed the mutant (named as Def-A) in Escherichia coli, and analyzed the mutant's activity, structure, and dynamics. Def-A is active against several bacterial strains, but the activity is influenced by the ionic strength of the environment. When subjected to vesicles like POPG or to micelles like SDS, Def-A is changed from a random coil structure to an ordered helical form. We have determined the structure of Def-A in SDS micelle and found that it is folded into two distinct helices separated by a proline kink. We propose that the long N-terminal helix with many hydrophobic residues is inserted inside the micelle while the C-terminal helix with one large positive charge patch is located outside the micelle and interacts with the charged head groups of the micelle. The model is supported by NMR relaxation and H-D exchange data. Our results indicate that in addition to the number of positively charged residues and hydrophobic residues, the arrangement of these residues in the three-dimensional space is important to the antimicrobial selectivity and salt-dependent activity of human beta defensins.