Mutilation of RNA phage Qβ virus‐like particles: from icosahedrons to rods

Abstract
Icosahedral virus‐like particles (VLPs) of RNA phage Qβ are stabilized by four disulfide bonds of cysteine residues 74 and 80 within the loop between β‐strands F and G (FG loop) of the monomeric subunits, which determine the five‐fold and quasi‐six‐fold symmetry contacts of the VLPs. In order to reduce the stability of Qβ VLPs, we mutationally converted the amino acid stretch 76‐ANGSCD‐81 within the FG loop into the 76‐VGGVEL‐81 sequence. It led to production in Escherichia coli cells of aberrant rod‐like Qβ VLPs, along with normal icosahedral capsids. The length of the rod‐like particles exceeded 4–30 times the diameter of icosahedral Qβ VLPs.