Shape-Morphing of an Artificial Protein Cage with Unusual Geometry Induced by a Single Amino Acid Change

Abstract

Artificial protein cages are constructed from multiple protein subunits. The interaction between the subunits, notably the angle formed between them, controls the geometry of the resulting cage. Here, using the artificial protein cage, “TRAP-cage”, we show that a simple alteration in the position of a single amino acid responsible for Au­(I)-mediated subunit–subunit interactions in the constituent ring-shaped building blocks results in a more acute dihedral angle between them. In turn, this causes a dramatic shift in the structure from a 24-ring cage with an octahedral symmetry to a 20-ring cage with a C2 symmetry. This symmetry change is accompanied by a decrease in the number of Au­(I)-mediated bonds between cysteines and a concomitant change in biophysical properties of the cage.

Near-Miss Bi-Homogenous Symmetric Polyhedral Cages

“…The other six holes are made from the edges of four hendecagonal faces, which contribute to the holes with two of their edges. Some similar nearly regular structures made of the same protein have been recently identified [5,6].…”

“…One must therefore find all the i and f i satisfying (6). Then, compute V 1 and V 2 using (3), which must be integers, and compute v 1,i and v 2,i using (7), which must also be integers that satisfy (8).…”

“…The structure of virus capsids is essentially based on the geometry of platonic solids [33]. Some of the cages created experimentally, on the other hand, exhibit structures that are completely different [2,5,6]. This raises the question as to which are the best geometries for such cages [34][35][36].…”

An artificial protein cage made from a 12-membered ring

“…1(e)). 16 If we consider the TRAP ring as a highly truncated cone, this moved the position of the cysteines on the outer circumference of TRAP further toward the narrow end of the cone. These modified TRAP rings were still able to form TRAP-cages upon mixing with gold( i ).…”

Design of a symmetry‐broken tetrahedral protein cage by a method of internal steric occlusion

“…Recent efforts have also succeeded in generating an asymmetric holey viral capsid through a set of featurespecific hierarchical assembly steps of subunits with designed asymmetry (Zhao et al, 2021). Furthermore, it has been possible to change the symmetry of protein cages by point mutations that alter their subunit-subunit interactions (Sharma et al, 2022;Szyszka et al, 2024). Nonetheless, self-assembly design methods, whose successes are dramatically expanding due to modern machine learning algorithms (de Haas et al, 2023;Meador et al, 2023), generally give rise to symmetric architectures, and thus to challenges in breaking symmetry for certain purposes.…”