No abstract

Engineering proteins to construct self-assemblies is of crucial significance not only for understanding the sophisticated living systems but also for fabricating advanced materials with unexplored functions. However, due to the inherent chemical heterogeneity and structural complexity of the protein surface, designing complex protein assemblies in an anisotropic fashion remains challenging. Here, we describe a self-assembly approach to fabricating protein origami with a networklike structure by designing dual noncovalent interactions on the different positions of a single protein building block. With dimeric proteins as building blocks, 1D protein filaments were constructed by the designed metal coordination at key protein interfaces. Subsequently, the network superstructures were created by the cross-linking of the 1D protein filaments at branch point linkages through the second designed π−π stacking interactions. Notably, upon increasing the protein concentration, the formed protein networks convert into hydrogels with reversible, injectable, and self-healing properties, which have the ability to promote bone regeneration. This strategy could be used to fabricate other protein-based materials with unexplored functions.

The slow catalytic rate of the carboxylation enzyme D-ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is a major barrier to increasing the rate of carbon assimilation from the atmosphere into the biosphere. It is of great importance to establish a method to improve the carboxylation efficiency of Rubisco. Inspired by the assembly of Rubisco in carboxysomes, herein, we presented a rational protein engineering approach for the construction of one-dimensional (1D) protein arrays of type III Rubisco through designed π−π stacking interactions by using crystal structural information as a guide. In aqueous solutions, the dimensions of these 1D protein arrays collectively span nearly the entire nano-and micrometer scale (200 nm to 5.0 μm) by adjusting protein and NaCl concentrations. As a result, the stacked Rubisco assemblies increase by 40% in the carboxylase activity, while their turnover number (k cat ) is around twofold larger than that of wild-type III Rubisco. Notably, upon heat treatment at temperature up to 75 °C for 30 min, most of the assembled nanostructures and the enzyme activity are retained. More importantly, the initial relative activity of stacked assemblies retained 91% after 10 cycles of reuse. This work provides a simple, effective solution for the improvement of the CO 2 carboxylation efficiency of Rubisco.

CO 2 mineralization by colloidal nanoclusters of MgO or CaO represents one effective way to reduce its levels in the atmosphere. However, a high temperature (>200 °C) is required for this process. Herein, we found that the Mg 2+ -mediated Thermotoga maritima ferritin (TmFtn) nanocage has the ability to convert CO 2 (3.128 mmol per gram of protein) into MgCO 3 nanoparticles in an aqueous solution with Mg 2+ as starting materials at room temperature, but the rate of such bioconversion is relatively slow. To improve the CO 2 conversion efficiency, we constructed a two-compartment system based on threedimensional (3D) protein crystalline frameworks by using dimeric TmFtn as building blocks, which consists of two types of compartments, namely, small ferritin cavity and large interglobular space. By using the system, directed compartmentalization of Mg 2+ and carbonic anhydrase (CA) according to their difference in size can be realized using a one-pot method. Consequently, the CO 2 conversion value of the CA-encapsulated protein crystalline frameworks reaches as high as around 8.485 mmol per gram of protein, while the conversion rate increases by 2 to 3 times. Notably, its reversible disassembly and reassembly property endows the frameworks with satisfied recyclability, allowing them to be suitable for practical applications.

Zinc binding strength of diet proteins dominants zinc uptake in Caco-2 cells.