Self-Assembly of Proteinaceous Multishell Structures Mediated by a Supercharged Protein

Area of Science:

• Biochemistry
• Nanotechnology
• Structural Biology

Background:

• Engineered protein cages, like lumazine synthase variants, can encapsulate macromolecules via electrostatic interactions.
• Controlling the assembly of these protein cages is crucial for developing novel nanostructures.

Purpose of the Study:

• To investigate the influence of ionic strength and cargo molecules on the assembly of AaLS-13, a negatively supercharged lumazine synthase protein cage.
• To explore the formation of multishell protein structures using electrostatic interactions.

Main Methods:

• Assembly of AaLS-13 protein cages with varying ionic strengths.
• Incorporation of a positively supercharged green fluorescent protein variant (GFP(+36)) as a charged mediator.
• Analysis of the resulting multishell structures and their dependence on ionic strength.

Main Results:

• Multishell structures of AaLS-13 were successfully produced by mixing with free capsomers and GFP(+36).
• Assembly is highly dependent on ionic strength due to electrostatic interactions between the negatively charged cage and positively charged GFP(+36).
• Unlike viral multishells, the positively charged mediator was essential for forming diverse multilayered structures.

Conclusions:

• Electrostatic interactions and ionic strength are critical factors in controlling the assembly of engineered protein cages.
• A mediator-bridging approach using charged guest molecules enables the creation of hierarchical protein nanostructures.
• This method holds promise for applications in drug delivery and bioimaging.