APBN New Site

APBN Developing Site

Unravelling Protein Assembly Dynamics With Artificial Protein Needles

Scientists believe that this newly developed, specialised protein needle can help us uncover new clues about protein microstructures and assembly processes.

Proteins are widely considered to be one of the most basic building blocks of our bodies, but their molecular and macroscopic structures are highly complex and diverse, with multiple folding patterns and substructures. To build supramolecular structures and functional bio-nanomaterials, scientists have long strived to unravel proteins and analyse the way in which they assemble. They have made use of atomic force microscopy, fluorescence microscopy, and high-speed atomic force microscopy in the hope of finding clues for controlling the dynamic process of protein self-assembly. Unfortunately, scientists have yet to clarify the assembly mechanism of proteins as they have not been able to directly observe the anisotropic motion of proteins during formation.

Now, scientists at the Tokyo Institute of Technology have collaborated with Kyushu University, Nagoya University, and National Institutes of Natural Sciences and developed a specialised anisotropic protein needle that can help determine the assembly of similarly anisotropic proteins and bring new insights into their microstructure. By regulating the tip-to-tip interactions of these needles, they allow for the self-assembly of proteins and the controlled construction of various protein architectures.

“Our [protein needle] is a needle-shaped protein composed of the rigid body (β-helix), the terminal cap (foldon), and a binding motif (hexa-histidine tag, His-tag). By modifying these [protein needles] by deleting the His-tag motif and foldon cap, we can produce three different types of [protein needles]. This enabled us to regulate and observe different assembly patterns and how they change, giving us clues into the mechanics of different protein-protein interactions that we find in nature,” explained Professor Takafumi Ueno of Tokyo Tech, who led the study.

In solution, the protein needles can spontaneously form a highly stable structure that is about 20 nm long and 3.5 nm wide. The structure is not only small enough to track the rotational motion of individual molecules, but is also mechanically strong. On a mica surface, the researchers found that the protein needle can self-assemble into various kinds of ordered structures such as fibre assemblies, ordered monomeric states, and triangular lattices.

Through a combination of high-speed atomic force microscopy and Monte Carlo simulations, the researchers were also able to use the protein needles to analyse the dynamic processes involved in protein assembly. Their findings showed that the formation of the triangular lattice structure was guided by the dynamic motions of the protein needle, which contribute to the formation of ordered lattices.

Given these results, the scientists are excited about the potential applications and implications of their innovation. Their work is expected to lay the foundation for controlling directional interactions of anisotropic shaped proteins and constructing a variety of supramolecular protein architectures.

“These molecules play such a crucial role in biological systems that understanding their structure would further the field significantly. For instance, we could use this to lay the groundwork for constructing supramolecular structures by designing the dynamic collective motions of proteins. This concept can lead to the engineering of biocompatible sheet materials, targeted drug transports, and even protein-based nano-robots,” commented Professor Ueno. [APBN]

Source: Kikuchi et al (2022). Protein Needles Designed to Self-Assemble through Needle Tip Engineering. Small, p. 2106401.