Mutant Viruses from Hell: Comparing the Capsid Structure of VP1 Mutants to the Wild-Type

Viruses can be defined as genetic material tightly packed in a protein coat called the capsid. The spindle-shaped fuselloviruses are found worldwide in hot springs at over 80°C and below pH 4. Sulfolobus spindle-shaped virus 1 (SSV1) is a fusellovirus known to infect the archaea, Saccharolobus solfataricus. This research will provide further insights into the survival of macromolecules, particularly proteins, that are present in extreme environments. To study the interaction of proteins within these extreme environments, we are studying the capsid structure of SSV1. The capsid of SSV1 is composed of two main proteins, VP1 (major) and VP3 (minor). There is a proteolytic cleavage site in the VP1 protein, glutamate (E) in position 66 (E66), which is highly conserved in fuselloviruses. To determine the importance of the amino acid at this position, we have mutated the wild-type amino acid to multiple different amino acids—isoleucine, glutamine, methionine, serine, and phenylalanine—using site-directed mutagenesis. In this study, we intend to determine if a change to the normally occurring glutamate affects the capsid structure. The mutants have been imaged with transmission electron microscopy and analyzed with ImageJ, to identify differences in length and width of the capsid, followed by statistical analyses to determine any significant statistical differences in size and shape between these mutants. Conducting more research on the VP1 capsid protein furthers our understanding of how the virus and its proteins maintain structural integrity in extreme environments, which may have broader applications in biomedical applications and nanotechnology.