Colorful Virus-like Particles: Fluorescent Protein Packaging by the Qβ Capsid

Abstract

Qβ virus-like particles encapsulating multiple copies of fluorescent proteins were generated in high yields using a modular system enhanced by specific engineered RNA-protein interactions. The resulting particles were structurally indistinguishable from recombinant Qβ alone. The encapsidated proteins were nearly identical in photochemical properties to monomeric analogues, were more stable toward thermal degradation, and were protected from proteolytic cleavage. Residues on the outer capsid surface were chemically derivatized by acylation and azide-alkyne cycloaddition without affecting the fluorescence properties of the packaged proteins. A high affinity carbohydrate-based ligand of the CD22 receptor was thereby attached, and specific cell labeling by the particles was successfully detected by flow cytometry and confocal laser microscopy.

Generation and characterization of a trackable plant-made influenza H5 virus-like particle (VLP) containing enhanced green fluorescent protein (eGFP)

“…A wide range of trackable VLPs has been generated by labeling one or more viral components with a fluorescent protein (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40). Many VLPs have been labeled after particle production/ purification, usually by chemical coupling to (in)organic Figure 2.…”

“…Designing genetically labeled VLPs that target nonenveloped viruses is conceptually not trivial as a result of the additional structural constraints (i.e., complex capsomer-folding events, increased rigidity, smaller size) (72), particularly if the cargo is to be placed inside the particle. These reagents do exist, however, despite the added complications (28,37). Such a panel of trackable, plantderived chimeric proteins and VLP reagents would be powerful tools to study VLP biology, both in the plant itself (e.g., protein expression and folding, internal tracking, particle assembly and budding) and in the mammalian immune system (e.g., trafficking, cell association, disassembly).…”

Transient Contacts on the Exterior of the HK97 Procapsid That Are Essential for Capsid Assembly

“…The HK97 fold has been detected in every tailed phage capsid that has been imaged at sufficient resolution, including P22 11; 12; 13 , T4 14 , λ 15 , ϕ29 16 , T5 17; 18 , P2/P4 19 , epsilon15 20 , T7 21; 22 , the tailed-phage-like archaevirus HSTV-1 23 , in the base layer of the Herpesvirus (HSV1) major capsid protein 24 and in the bacterial comparments known as encapsulins 25 . With renewed interest in phage therapy to combat multiple-drug-resistant bacterial pathogens 26; 27; 28 , and an emerging interest in using bacteriophage capsids as platforms for nanotechnology 29 (http://www.nano.gov/) directed to the treatment of disease 30; 31 and the creation of new technologies 32; 33; 34; 35 , it is important to have a deep understanding of capsid structures and assembly pathways in order that they can be manipulated and utilized to the greatest extent.…”

Natural supramolecular building blocks: from virus coat proteins to viral nanoparticles

“…Moreover, such re-assembly processes can be mediated by a variety of foreign materials, such as nucleic acids, liquid droplets, polymers, enzymes, nucleic-acid functionalized particles, and other ligand-coated particles. By using such strategies, the VLPs may efficiently encapsulate functional materials within the protein capsids or display functional groups on the exterior surface, which therefore show great promise in many application fields including light harvesting, [41][42][43][44] imaging, 45 diagnosis 46 and catalysis. [47][48][49] …”