Guanghua Zhao

Hemocyanin is a giant oxygen transporter widely distributed in invertebrates, belonging to the type 3 copper protein family. However, its met state form with the detailed structural information and other functions has not yet been determined. In this study, we established a new purification method to isolate the purple functional unit of type 1 hemocyanin from abalone (Haliotis discushannai) (HtH1-h). The molecular-level structure of HtH1-h was determined by X-ray crystallography at resolution of 2.0 Å. Two distinct oxygen-binding states have been captured within the HtH1-h homodimer (Oxygenation state and Met state), which provides the first structural case of the met state of hemocyanin. Additionally, enzymatic characterization revealed detectable diphenolase activity in HtH1-h, whereas monophenolase activity was not observed. These findings suggest that hemocyanin might be an active protein with multiple functions.

Efficient noble-metal-free photosynthesis systems for CO2 conversion based on earth-abundant elements have been largely unexplored. On the other hand, large quantities of bovine blood as waste byproducts during meat processing pose environmental challenges. To address these concerns, herein we report a biomimetic photocatalytic platform constructed by hemoglobin, a major component in bovine blood, which structurally and functionally emulates the fibrous chloroplasts of Spirogyra. Under denaturing conditions, hemoglobin molecules self-assemble into heme-containing amyloid-like fibrils, in which the intrinsic heme groups serve as visible-light photosensitizers. Subsequently, iron-based catalytic cores are uniformly deposited along the protein fibrils, generating a hierarchical architecture that integrates heme as a light-harvesting domain and iron cores as catalytic functionalities within a single scaffold. This spatially organized system effectively shortens electron transfer distances and promotes interfacial charge migration. Consequently, the as-prepared biomimetic assembly exhibits efficient visible-light-driven CO2 reduction to formic acid with high activity and selectivity as compared to conventional homogeneous systems. Notably, this work not only provides a noble-metal-free strategy for constructing integrated photocatalytic systems but also demonstrates a viable pathway for transforming biological waste into high-value functional materials.

Although ferritin, as a versatile nanocarrier, has been engineered to improve cargo loading efficiency for various functions, including therapeutic applications, a universal design strategy enabling tunable molecular binding remains an unmet challenge. This study reports an AI‐aided structure‐guided engineering approach targeting the ferroxidase center of recombinant human heavy‐chain ferritin (rHuHF), aiming to achieve either universal molecular binding or high‐affinity specific recognition. Through site‐directed mutagenesis of key residues within and flanking the ferroxidase center, two rHuHF variants (rHuHF‐C1 and rHuHF‐C2) were generated. X‐ray crystallographic analysis revealed that the engineered pocket within rHuHF‐C2 can accommodate a broad range of hydrophobic molecules (e.g., Curcumin, CUR) via hydrophobic interactions, thus validating their universal molecular binding capability. On the other hand, leveraging AI‐assisted rational design, a variant (rHuHF‐71) was subsequently engineered to specifically bind CUR with enhanced affinity, facilitated by the formation of hydrogen bonds and optimized hydrophobic contacts. This work establishes a generalizable strategy, designated as “Excavation, Rebuilding, and Validation”, for engineering ferritin nanocages with tunable binding specificities, which holds great promise for advancing the development of protein‐based drug delivery systems and the design of small‐molecule binding proteins.

Reconstituting natural pigment complexes in vitro enables dissection of their formation and color-tuning mechanisms, but remains challenging. Here we reconstructed the thermochromic pigment of the prawn Macrobrachium rosenbergii by a ternary coassembly of recombinant lipocalin rMrLC, astaxanthin and phospholipid. The complex is blue at room temperature with a bathochromic shift of 130 nm relative to free astaxanthin and turns orange-red upon heating, a property matching the natural pigment. The crystal structures of both apo rMrLC and the ternary complex reveal that the binding of astaxanthin to the protein causes a closed-to-open state transition, producing the ternary complex where a homodimeric lipocalin scaffold clamps a sandwich-like astaxanthin–phospholipid–astaxanthin core. Structural analyses, coupled with site-directed mutagenesis, spectroscopy and quantum mechanics/molecular mechanics calculations elucidate the formation and color-tuning mechanism of the blue complex. This work establishes design principles for engineering tunable protein-based pigments and color-changing biomaterials.