SPECIFICITY IN SELF-ASSEMBLY OF BACTERIOPHAGES QBETA AND MS2

Using purified ribonucleic acid and protein components of two serologically and electrophoretically distinct phages Qβ and MS2, phage-like particles were readily assembled from homologous ribonucleic acid and protein as well as from heterologous components. The hybrid particles were antigenically and electrophoretically similar to the homologous particles and to the authentic phages having the same protein component. The reassembled particles produced from all four ribonucleic acid and protein combinations had similar sedimentation properties in sucrose density gradient. They differed in that the hybrids had no or very low infectivity as compared with the homologous reassembled particles. Under conditions where two phage ribonucleic acids competed for one phage protein, the formation of homologous particles prevailed; whereas when two proteins competed for one ribonucleic acid, Qβ protein was predominantly incorporated into particles with either ribonucleic acid. Particles with mixed protein coat were not detected. Thus the interaction between protein subunits appeared to have absolute species specificity. © 1969, American Chemical Society. All rights reserved.