Department of Structural Biology, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
Department of Infectious Diseases, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
Structure. 2015 Apr 7;23(4):713-23. doi: 10.1016/j.str.2015.01.020. Epub 2015 Mar 5.
Bacterial ATP-binding cassette (ABC) importers play critical roles in nutrient acquisition and are potential antibacterial targets. However, structural bases for their inhibition are poorly defined. These pathways typically rely on substrate binding proteins (SBPs), which are essential for substrate recognition, delivery, and transporter function. We report the crystal structure of a Staphylococcus aureus SBP for Mn(II), termed MntC, in complex with FabC1, a potent antibody inhibitor of the MntABC pathway. This pathway is essential and highly expressed during S. aureus infection and facilitates the import of Mn(II), a critical cofactor for enzymes that detoxify reactive oxygen species (ROS). Structure-based functional studies indicate that FabC1 sterically blocks a structurally conserved surface of MntC, preventing its interaction with the MntB membrane importer and increasing wild-type S. aureus sensitivity to oxidative stress by more than 10-fold. The results define an SBP blocking mechanism as the basis for ABC importer inhibition by an engineered antibody fragment.
细菌三磷酸腺苷结合盒（ABC）转运蛋白在营养物质获取中发挥着关键作用，是潜在的抗菌靶点。然而，它们的抑制作用的结构基础还未完全明确。这些途径通常依赖于底物结合蛋白（SBPs），其对于底物识别、传递和转运体功能至关重要。我们报告了金黄色葡萄球菌 Mn(II) SBP 的晶体结构，称为 MntC，与 FabC1 复合物的结构，FabC1 是 MntABC 途径的一种有效的抗体抑制剂。该途径在金黄色葡萄球菌感染过程中是必需的且高度表达，有助于 Mn(II)的导入，Mn(II)是解毒活性氧（ROS）的酶的关键辅因子。基于结构的功能研究表明，FabC1 从空间上阻断了 MntC 的一个结构保守表面，阻止其与 MntB 膜转运蛋白相互作用，并使野生型金黄色葡萄球菌对氧化应激的敏感性增加了 10 多倍。该结果定义了一种 SBP 阻断机制，为工程化抗体片段抑制 ABC 转运蛋白提供了理论基础。
