Solubilization of the Semliki Forest virus membrane with sodium dodecyl sulfate

The dissociation of Semliki Forest virus induced by increasing concentrations of the anionic detergent sodium dodecyl sulfate was studied using density gradient centrifugation. Detectable binding to the virus started well below the critical micellar concentration of the detergent and increased thereafter with increased detergent concentration. At 4 degrees there were about 11,000 binding sites per virus particle with an average association constant of about 10-5 M-1. The extent of virus dissociation could be controlled both by the detergent concentration and by the temperature. At 4 degrees only disruption ("lysis") of the virus membrane could be observed. At 20 degrees most of the membrane was solubilized into lipoprotein complexes, and the nucleocapsid dissociated into RNA and protein. Complete delipidation of the viral membrane proteins was achieved at 30 degrees at a detergent concentration still below the critical micellar concentration.