Self-assembled bionanoparticles based on the Sulfolobus tengchongensis spindle-shaped virus 1 (STSV1) coat protein as a prospective bioscaffold for nanotechnological applications.

Biomolecule-nanoparticle hybrid bioconjugates based on bioscaffolds such as protein cages and virus capsules have been widely studied. Highly stable and durable biotemplates are a vital pillar in constructing bio-inorganic functional hybrid composites. Here, we introduce a highly heat-resistant coat protein (CP) of Sulfolobus tengchongensis spindle-shaped virus 1 (STSV1) isolated from the hyperthermophilic archaeon as a prospective biological matrix. Our experiments showed that STSV1 CP was successfully cloned and solubly expressed in the Escherichia coli Rosetta-(DE3) host strain. Protein expression was verified by SDS-PAGE and western blot analysis of the reference C-terminally six-histidine (His6) tagged STSV1 CP (HT-CP). Thermal stability experiments showed that the STSV1 coat protein remained fairly stable at 80 °C. The proteins can be purified facilely by heat treatment followed by size exclusion chromatography (SEC). Transmission electron microscopy (TEM) analysis of the purified STSV1 CP protein aggregates demonstrated that the protein could self-assemble into rotavirus-like nanostructures devoid of genetic materials under our experimental conditions. Similar results were obtained for the HT-CP purified by heat treatment followed by Ni-NTA and SEC, indicating that moderately engineered STSV1 CP can retain its self-assembly property. In addition, the STSV1 CP has a high binding affinity for TiO2 nanoparticles. This illustrates that the STSV1 CP can be used as a bioscaffold in nanobiotechnological applications.