Facile Purification and Use of Tobamoviral Nanocarriers for Antibody-Mediated Display of a Two-Enzyme System.

Immunosorbent turnip vein clearing virus (TVCV) particles displaying the IgG-binding domains D and E of Staphylococcus aureus protein A (PA) on every coat protein (CP) subunit (TVCVPA) were purified from plants via optimized and new protocols. The latter used polyethylene glycol (PEG) raw precipitates, from which virions were selectively re-solubilized in reverse PEG concentration gradients. This procedure improved the integrity of both TVCVPA and the wild-type subgroup 3 tobamovirus. TVCVPA could be loaded with more than 500 IgGs per virion, which mediated the immunocapture of fluorescent dyes, GFP, and active enzymes. Bi-enzyme ensembles of cooperating glucose oxidase and horseradish peroxidase were tethered together on the TVCVPA carriers via a single antibody type, with one enzyme conjugated chemically to its Fc region, and the other one bound as a target, yielding synthetic multi-enzyme complexes. In microtiter plates, the TVCVPA-displayed sugar-sensing system possessed a considerably increased reusability upon repeated testing, compared to the IgG-bound enzyme pair in the absence of the virus. A high coverage of the viral adapters was also achieved on Ta2O5 sensor chip surfaces coated with a polyelectrolyte interlayer, as a prerequisite for durable TVCVPA-assisted electrochemical biosensing via modularly IgG-assembled sensor enzymes.

In vivo self-assembly of TMV-like particles in yeast and bacteria for nanotechnological applications.

Heterologous expression of tobacco mosaic virus coat protein and in vivo assembly of rod-shaped TMV-like particles encapsidating viral or host RNA were compared between Escherichia coli and Schizosaccharomyces pombe. TMV-like particles were produced in both hosts, irrespective of whether the TMV origin of assembly was present. The additional plasmid providing an OAS-containing RNA was able to alter the length distribution of the TMV-like particles. Plant and yeast-expressed CP behaved similarly upon isoelectric focusing, whereas CP expressed in bacteria migrated differently. After purification by buoyant density centrifugation, the encapsidated nucleic acids were determined to be of host origin as well as of viral origin. OAS-containing mRNA was packaged preferentially in yeast to some extent (8%). In consequence, the majority of TMV-like particles showed the same length distribution similar to those in the absence of OAS-containing mRNA, likely due to host RNA being primarily encapsidated. Notwithstanding this limitation for tailoring particle sizes, the heterologous expression system provides a new avenue to deliver versatile nucleoprotein scaffolds for a diversity of nanotechnological applications, without the need for an infectious virus. The results are discussed with reference to the competition of translation and packaging as well as to the selective decay of TMV RNA.

Inducible site-selective bottom-up assembly of virus-derived nanotube arrays on RNA-equipped wafers.

Tobacco mosaic virus (TMV) is a tube-shaped, exceptionally stable plant virus, which is among the biomolecule complexes offering most promising perspectives for nanotechnology applications. Every viral nanotube self-assembles from a single RNA strand and numerous identical coat protein (CP) subunits. Here we demonstrate that biotechnologically engineered RNA species containing the TMV origin of assembly can be selectively attached to solid surfaces via one end and govern the bottom-up growth of surface-linked TMV-like nanotubes in situ on demand. SiO(2) wafers patterned by polymer blend lithography were modified in a chemically selective manner, which allowed positioning of in vitro produced RNA scaffolds into predefined patches on the 100-500 nm scale. The RNA operated as guiding strands for the self-assembly of spatially ordered nanotube 3D arrays on the micrometer scale. This novel approach may promote technically applicable production routes toward a controlled integration of multivalent biotemplates into miniaturized devices to functionalize poorly accessible components prior to use. Furthermore, the results mark a milestone in the experimental verification of viral nucleoprotein complex self-assembly mechanisms.

In vitro assembly of Tobacco mosaic virus coat protein variants derived from fission yeast expression clones or plants.

Tobacco mosaic virus (TMV) derivatives are explored currently extensively with regard to nanotechnological applications. Since certain technically desired TMV mutants may not be accessible from plants, the utility of the fission yeast Schizosaccharomyces pombe for heterologous production of TMV coat protein (CP) variants was explored, including wild-type (wt) CP and two genetically engineered mutants: TMV-CP-His(6) containing a C-terminal hexahistidine (His(6)) tag, and TMV-CP-E50Q with enhanced lateral CP subunit interactions. After establishing expression clones and protocols for enrichment of the CP variants, their ability to reconstitute TMV-like nanostructures in the presence or absence of RNA was tested in comparison with the corresponding plant-derived CP variants, which were expressed from infectious TMV constructs. Both TMV-CP-E50Q and TMV-CP-wt yielded TMV-like rods, irrespective of the proteins' source. In contrast, His-tagged CP from plants produced only short rods in an inefficient manner, and no rods at all when expressed in yeast. This study introduces a novel approach to produce assembly competent TMV CP, but also demonstrates its limitations.

Atomic layer deposition on biological macromolecules: metal oxide coating of tobacco mosaic virus and ferritin.

Decoration of nanoparticles, in particular biomolecules, gathered high attention in recent years.(1-7) Of special interest is the potential use of biomolecules as templates for the fabrication of semiconducting or metallic nanostructures.(1-7,26) In this work we show the application of atomic layer deposition, a gas-phase thin film deposition process, to biological macromolecules, which are frequently used as templates in nanoscale science, and the possibility to fabricate metal oxide nanotubes and thin films with embedded biomolecules.(1-13).