Mutilation of RNA phage Q beta virus-like particles: from icosahedrons to rods

Icosahedral virus-like particles (VLPs) of RNA phage Q beta are stabilized by four disulfide bonds of cysteine residues 74 and 80 within the loop betw een beta-strands F and G (FG loop) of the monomeric subunits, which determi ne the five-fold and quasi-six-fold symmetry contacts of the VLPs. In order to reduce the stability of Q beta VLPs, we mutationally converted the amin o acid stretch 76-ANGSCD-81 within the FG loop into the 76-VGGVEL-81 sequen ce. It led to production in Escherichia coli cells of aberrant rod-like Q b eta VLPs, along with normal icosahedral capsids. The length of the rod-like particles exceeded 4-30 times the diameter of icosahedral Q beta VLPs. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier S cience B.V. All rights reserved.