NTP BINDING INDUCES CONFORMATIONAL-CHANGES IN THE DOUBLE-STRANDED-RNABACTERIOPHAGE-O6 SUBVIRAL PARTICLES

Bacteriophage 06 is a double-stranded RNA virus consisting of a nucleo capsid (NC) surrounded by a membrane. Beneath the NC major coat protei n, P8, resides the 06 RNA polymerase complex which is composed of four early proteins P1, P2, P4, and P7. Protein P1 forms the dodecahedral framework with which the other three proteins are associated. We have developed a new method for the isolation of stable polymerase complex particles which retain their structural integrity and polymerase activ ity for several days. Purine nucleotides, especially GTP, dGTP, ddGTP, and GDP, stabilized the particle efficiently. Furthermore, binding of any NTP was shown to induce conformational changes in the NC structur e, as detected by alterations in the binding properties of NC-specific monoclonal antibodies. In the presence of NTPs, most of the epitopes in protein P4 become more exposed than without NTPs, while the epitope s in protein P8 were either masked or unmasked due to NTP binding. Bas ed on the accessibility of the epitopes of protein P1 on the NC, we po stulate that at least part of this protein is also accessible on the N C surface. (C) 1994 Academic Press, Inc.