The researchers succeeded in making protein nanotubes from small scaffolds.

Researchers at Tokyo Tech of Technology have succeeded in making protein nanotubes from small scaffolds made of cross-linked engineering crystal proteins. This achievement can accelerate the development of artificial enzymes, nanoscale carriers and delivery systems for biomedical and biotech applications.

A group led by Taken Ueno of Tokyo Tech's Biomolecular Engineering has developed an innovative way to assemble proteins into well-aligned nanotubes.

Custom protein nanostructures are of interest because they can be used to develop highly specific and powerful catalysts, targeted drug and vaccine delivery systems and many other promising biomaterials.

Scientists have been struggling to make protein assemblies in aqueous solutions because of the confusing manner in which proteins interact freely under a variety of conditions, such as pH and temperature.

New methods reported in journals Chemical scienceWe overcome this problem by using protein crystals that serve as promising scaffolds in which proteins can self-assemble into the desired structure. This method consists of four steps as described in the construction of nanotubes from protein crystals.

• Manufacture of engineering proteins
• Formation of protein crystal scaffold
• Formation of cross-linked crystals
• Dissolving the scaffold to release protein nanotubes.

The crystal structure consists of an ordered array of assembled structures, allowing cross-linking to easily control precise chemical interactions to stabilize the assembly structure. This is an accomplishment that can not be achieved by cross-linking proteins in solution.

The researchers chose a naturally occurring protein called RubisCO as a building block for the construction of nanotubes. Due to its high stability, RubisCO was able to maintain its shape and the crystal structure of previous studies was recommended in this study.

Using TEM (Transmission Electron Microscopy) imaging at Suzukakedai Biomaterials Analysis Division of Tokyo Tech, the team successfully identified the formation of protein nanotubes.

The study also demonstrated that protein nanotubes can maintain enzyme capacity.

"Our cross-linking method can efficiently promote the formation of a crystal support at a desired location (a particular cysteine ​​site) within each tube of the crystal," Ueno said. "Since more than 100,000 protein crystal structures are currently stored in the Protein Data Bank, our method can be applied to other protein determinations to build supramolecular protein assemblies such as ours, tubes and sheets."

Nanotubes can be used in a variety of applications in this research. Tubes provide an environment for the accumulation of exogenous molecules that can be used as a platform for delivery in the pharmaceutical field. This tube also has the potential to catalyze because protein building blocks have inherently enzymatic activity.