Histidine (His) residues represent versatile motifs for designing protein-protein interactions because the protonation state of the imidazole group of His is the only moiety in protein to be significantly pH dependent under physiological conditions. Here we show that, by the designed His motifs nearby the C₄ axes, ferritin nanocages arrange in crystals with a simple cubic stacking pattern. The X-ray crystal structures obtained at pH 4.0, 7.0, and 9.0 in conjunction with thermostability analyses reveal the strength of the π–π interactions between two adjacent protein nanocages can be fine-tuned by pH. By using the crystal structural information as a guide, we constructed 3D protein frameworks in solution by a combination of the relatively weak His–His interaction and Ni²⁺-participated metal coordination with Glu residues from two adjacent protein nanocages. These findings open up a new way of organizing protein building blocks into 3D protein crystalline frameworks.

组氨酸 (His) 残基代表用于设计蛋白质-蛋白质相互作用的通用基序，因为 His 的咪唑基团的质子化状态是蛋白质中唯一在生理条件下显着 pH 依赖性的部分。在这里，我们表明，通过在C ₄轴附近设计的 His 图案，铁蛋白纳米笼以简单的立方堆叠模式排列在晶体中。在 pH 4.0、7.0 和 9.0 下获得的 X 射线晶体结构与热稳定性分析相结合，揭示了两个相邻蛋白质纳米笼之间 π-π 相互作用的强度可以通过 pH 值进行微调。通过使用晶体结构信息作为指导，我们通过相对较弱的 His-His 相互作用和 Ni ^{2+的组合在溶液中构建了 3D 蛋白质框架}-参与金属与来自两个相邻蛋白质纳米笼的 Glu 残基的配位。这些发现开辟了一种将蛋白质构建块组织成 3D 蛋白质晶体框架的新方法。