Li Ming, Dong Xiaoyan, Liu Yang, Sun Yan
Department of Biochemical Engineering and Key Laboratory of Systems Bioengineering of the Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300354, P. R. China.
Department of Biology and Guangdong Provincial Key Laboratory of Marine Biotechnology, College of Science, Shantou University, Shantou, Guangdong, 515063, P. R. China.
Chem Asian J. 2017 May 18;12(10):1062-1068. doi: 10.1002/asia.201700058. Epub 2017 Apr 20.
A 39-amino acid peptide fragment that is derived from prostatic acidic phosphatase (PAP), PAP , is secreted in large amounts in human semen and forms amyloid fibrils. These fibrils can capture HIV virions and increase the attachment of virions to target cells; as such, they are called a "semen-derived enhancer of virus infection" (SEVI). Therefore, the inhibition of the formation of PAP amyloid fibrils is of great significance. Herein, we demonstrate that brazilin effectively inhibits PAP aggregation. The inhibitory effect increases with increasing brazilin concentration. Thioflavin T fluorescence assays and TEM observations confirmed that a few fibrils formed when brazilin was present with PAP in an equimolar concentration. Circular dichroism spectroscopy indicated that brazilin inhibited the secondary structural transitions from α-helices and random coils into β-sheets. Cytotoxicity assays showed that brazilin significantly decreased the cytotoxicity of the fibrils at 0.01 mmol L . Isothermal titration calorimetry revealed that hydrophobic interactions were the main driving force for the binding of brazilin to the PAP monomer (dissociation constant, 4.03 μmol L ), and that the binding affinity of brazilin for the fibrils was at least three orders of magnitude lower than that for the monomer. These results indicate that brazilin holds great potential as a small-molecule agent against SEVIs.
一种由前列腺酸性磷酸酶（PAP）衍生而来的39个氨基酸的肽片段，即PAP，在人类精液中大量分泌并形成淀粉样纤维。这些纤维可以捕获HIV病毒粒子并增加病毒粒子与靶细胞的附着；因此，它们被称为“精液衍生的病毒感染增强剂”（SEVI）。因此，抑制PAP淀粉样纤维的形成具有重要意义。在此，我们证明巴西苏木素能有效抑制PAP聚集。抑制作用随巴西苏木素浓度的增加而增强。硫黄素T荧光测定和透射电镜观察证实，当巴西苏木素与PAP以等摩尔浓度存在时，形成的纤维很少。圆二色光谱表明，巴西苏木素抑制了从α-螺旋和无规卷曲到β-折叠的二级结构转变。细胞毒性试验表明，在0.01 mmol·L时，巴西苏木素显著降低了纤维的细胞毒性。等温滴定量热法表明，疏水相互作用是巴西苏木素与PAP单体结合的主要驱动力（解离常数为4.03 μmol·L），且巴西苏木素对纤维的结合亲和力比对单体的结合亲和力至少低三个数量级。这些结果表明，巴西苏木素作为一种抗SEVI的小分子药物具有很大的潜力。
