# Biocatalytic 3D binary crystals formed through the self-assembly of enzyme-embedded ferritin

## TL;DR

Scientists created a new type of crystal using enzyme-filled protein cages that can act as reusable biocatalysts with controlled spatial arrangement.

## Contribution

A novel biocatalytic crystal is formed through enzyme-embedded ferritin nanocages with spatial control via electrostatic co-crystallization.

## Key findings

- Binary protein crystals with long-range order were formed using oppositely charged ferritin nanocages.
- The crystals retain enzymatic activity and can be reused in multiple catalytic cycles.
- This method enables the construction of multienzyme crystalline assemblies with spatially programmed biocatalysis.

## Abstract

Protein crystals are traditionally used to aid structural analysis but have recently gained attention as functional materials due to their intrinsic order, defined porosity, and high chemical programmability. While enzymes have been incorporated into protein crystals, most existing systems rely on post-crystallization loading or nonspecific adsorption, offering limited control over the spatial distribution of catalytic components. Furthermore, there are few examples of catalytically active crystals formed through the ordered assembly of protein nanocages. These modular and uniform building blocks provide precise size, surface chemistry, and cargo loading, making them ideal candidates for constructing functional crystalline materials. In this study, we report a binary protein crystal formed by electrostatic co-crystallization of oppositely charged ferritin nanocages, with one component encapsulating the peroxidase-mimicking enzyme enhanced ascorbate peroxidase 2 (APEX2). The resulting material exhibits long-range order, retains enzymatic activity, and can be reused in multiple catalytic cycles. This platform provides a framework for building multienzyme crystalline assemblies and studying spatially programmed biocatalysis.

Enzyme-embedded protein cage crystals are formed via electrostatic co-crystallization, enabling reusable biocatalytic assemblies with spatial control.