Protein nanocages have emerged as popular nanocarriers for either drug delivery or biotemplates for the preparation of nanomaterials. However, only three interfaces, namely exterior surface, intersubunit and inner cavity, have been used as reaction sites for the above purposes with all known protein nanocages. On the other hand, how to control the site of Au NCs formed within a targeted protein template while maintaining the functionality of protein itself remains challenging. In this work, inspired by compartmentalization in living systems, we firstly come up with the conception of “intrasubunit interfaces”, located within subunit of protein nanocage. We built a new, specific compartment for fabrication of gold nanoclusters by genetic modification of the inherent ferroxidase center located within four-α-helix bundle of each ferritin subunit. This newly built compartment not only realizes the site-directed synthesis of gold nanoclusters but also has no effect on the functionality of ferritin itself such as encapsulation by its inner cavity. These redesigned composites can be further applied as fluorescent imaging agent and carriers for preparation of hybrid nanomaterials. The designing strategy of intrasubunit interfaces opens a new way for future applications of cage-like proteins.

中文翻译：

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铁蛋白纳米笼亚基内界面内金纳米簇的设计和定点划分


蛋白质纳米笼已成为药物输送或制备纳米材料的生物模板的流行纳米载体。然而，只有三个界面，即外表面、亚基间和内腔，已被用作与所有已知的蛋白质纳米笼实现上述目的的反应位点。另一方面，如何控制目标蛋白质模板内形成的 Au NC 的位点，同时保持蛋白质本身的功能仍然具有挑战性。在这项工作中，受生命系统分隔的启发，我们首先提出了“亚基内界面”的概念，位于蛋白质纳米笼的亚基内。我们通过对位于每个铁蛋白亚基的四-α-螺旋束内的固有亚铁氧化酶中心进行遗传修饰，构建了一个新的、用于制造金纳米簇的特定隔室。这种新建的隔室不仅实现了金纳米团簇的定点合成，而且其内腔的封装等对铁蛋白本身的功能没有影响。这些重新设计的复合材料可以进一步用作荧光成像剂和载体来制备杂化纳米材料。亚基内界面的设计策略为笼状蛋白的未来应用开辟了新的途径。