Structure of the lipid-containing bacteriophage phi 6. Disruption by Triton X-100 treatment

The structure of the lipid-containing bacteriophage phi 6 was studied by means of controlled Triton X-100 disruption and subsequent isolation of subviral particles. Rate-zonal centrifugation yielded two fractions, a nucleocapsid fraction with RNA, proteins P1, P2, P4, P7, P8, and about half of the protein P5 and a membrane fraction with associated proteins P3, P6, P9, P10, and the rest of the protein P5. Following isopycnic sucrose gradient centrifugation, an empty capsid fraction was obtained which lacked RNA but contained a protein composition similar to the nucleocapsid except for the absence of P5. The membrane fraction isolated after isopycnic centrifugation was morphologically indistinguishable from that isolated after rate-zonal centrifugation but contained only proteins P3, P6, P9 and P10. By treating phi 6 with Triton X-100 prior to isopycnic sucrose gradient centrifugation the viral membrane was further separated into submembrane structures and the attachment protein, P3, could be isolated in rather pure form.