School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Queensland, Australia.
Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Queensland, Australia.
mBio. 2021 Feb 2;12(1):e01958-20. doi: 10.1128/mBio.01958-20.
Zinc is an essential element in all domains of life. Nonetheless, how prokaryotes achieve selective acquisition of zinc from the extracellular environment remains poorly understood. Here, we elucidate a novel mechanism for zinc-binding in AdcA, a solute-binding protein of Crystal structure analyses reveal the two-domain organization of the protein and show that only the N-terminal domain (AdcA) is necessary for zinc import. Zinc binding induces only minor changes in the global protein conformation of AdcA and stabilizes a highly mobile loop within the AdcA domain. This loop region, which is conserved in zinc-specific solute-binding proteins, facilitates closure of the AdcA binding site and is crucial for zinc acquisition. Collectively, these findings elucidate the structural and functional basis of selective zinc uptake in prokaryotes. Zinc is an essential nutrient for the virulence of bacterial pathogens such as Many Gram-positive bacteria use a two-domain lipoprotein for zinc acquisition, but how this class of metal-recruiting proteins acquire zinc and interact with the uptake machinery has remained poorly defined. We report the first structure of a two-domain lipoprotein, AdcA from , and use computational, spectroscopic, and microbiological approaches to provide new insights into the functional basis of zinc recruitment. Our findings reveal that AdcA employs a novel mechanism for zinc binding that we have termed the "trap-door" mechanism, and we show how the static metal-binding site of the protein, which confers its selectivity for zinc ions, is combined with a dynamic surface element to facilitate zinc recruitment and import into the bacterium. Together, these findings expand our understanding of how bacteria acquire zinc from the environment and provide a foundation for inhibiting this process, through antimicrobial targeting of the dynamic structural elements to block bacterial zinc scavenging.
锌是所有生命领域的必需元素。然而，原核生物如何从细胞外环境中选择性地获取锌仍然知之甚少。在这里，我们阐明了 AdcA 中锌结合的一种新机制，AdcA 是一种溶质结合蛋白。晶体结构分析揭示了该蛋白的两域结构，并表明只有 N 端结构域（AdcA）是锌导入所必需的。锌结合仅使 AdcA 的整体蛋白构象发生微小变化，并稳定了 AdcA 结构域内一个高度移动的环。该环区域在锌特异性溶质结合蛋白中保守，有利于 AdcA 结合位点的闭合，对锌获取至关重要。总之，这些发现阐明了原核生物选择性摄取锌的结构和功能基础。锌是细菌病原体如 许多革兰氏阳性菌使用一种两域脂蛋白来获取锌，但这类金属招募蛋白如何获取锌并与摄取机制相互作用仍不清楚。我们报告了来自 的两域脂蛋白 AdcA 的首个结构，并使用计算、光谱和微生物学方法提供了对锌招募功能基础的新见解。我们的发现揭示了 AdcA 采用了一种新的锌结合机制，我们称之为“活板门”机制，并展示了如何将该蛋白的静态金属结合位点（赋予其对锌离子的选择性）与动态表面元件结合，以促进锌的招募和导入细菌。这些发现共同扩展了我们对细菌如何从环境中获取锌的理解，并为通过针对动态结构元件的抗菌靶向来阻止细菌锌掠夺提供了基础。
