Department of Bioscience, Graduate School of Agriculture, Kinki University, Nara, Japan.
J Antibiot (Tokyo). 2010 Feb;63(2):89-94. doi: 10.1038/ja.2009.128. Epub 2010 Jan 8.
The WalK (a histidine kinase)/WalR (a response regulator, aka YycG/YycF) two-component system is indispensable in the signal transduction pathway for the cell-wall metabolism of Bacillus subtilis and Staphylococcus aureus. The inhibitors directed against WalK would be expected to have a bactericidal effect. After we screened 1368 culture broths of Streptomyces sp. by a differential growth assay, walkmycin A, B and C, which were produced by strain MK632-100F11, were purified using silica-gel column chromatography and HPLC. In this paper, the chemical structure of the major product (walkmycin B) was determined to be di-anthracenone (C(44)H(44)Cl(2)O(14)), which was very similar to BE40665A. MICs of walkmycin B against B. subtilis and S. aureus were 0.39 and 0.20 microg ml(-1), and IC(50) measurements against WalK were 1.6 and 5.7 microM, respectively. To clarify the affinity between WalK and walkmycin B, surface plasmon resonance was measured to obtain the equilibrium dissociation constant, K(D1), of 7.63 microM at the higher affinity site of B. subtilis WalK. These results suggest that walkmycin B inhibits WalK autophosphorylation by binding to the WalK cytoplasmic domain.
WalK（组氨酸激酶）/WalR（响应调节剂，又名 YycG/YycF）双组分系统是枯草芽孢杆菌和金黄色葡萄球菌细胞壁代谢信号转导途径中不可或缺的。针对 WalK 的抑制剂有望具有杀菌作用。在通过差异生长测定筛选了 1368 个链霉菌培养物后，由菌株 MK632-100F11 产生的 walkmycin A、B 和 C 通过硅胶柱色谱和 HPLC 进行了纯化。在本文中，主要产物（walkmycin B）的化学结构被确定为二蒽酮（C(44)H(44)Cl(2)O(14)），与 BE40665A 非常相似。walkmycin B 对枯草芽孢杆菌和金黄色葡萄球菌的 MIC 分别为 0.39 和 0.20 μg ml(-1)，对 WalK 的 IC(50)测量值分别为 1.6 和 5.7 μM。为了阐明 WalK 和 walkmycin B 之间的亲和力，通过表面等离子体共振测量获得了枯草芽孢杆菌 WalK 较高亲和力位点的平衡解离常数 K(D1)为 7.63 μM。这些结果表明 walkmycin B 通过与 WalK 细胞质结构域结合来抑制 WalK 自身磷酸化。
