Structural studies of the enveloped dsRNA bacteriophage phi 6 of Pseudomonas syringae by Raman spectroscopy. II. Nucleocapsid structure and thermostability of the virion, nucleocapsid and polymerase complex.

摘要: Structures and thermostabilities of the double-stranded (ds) RNA bacteriophage phi 6 its isolated nucleocapsid-polymerase complex (nucleocapsid core) dsRNA components have been investigated by Raman spectroscopy. The spectra show that proteins virion are collectively deficient in beta-sheet secondary structure. In particular, major protein (P8) outer spherical shell nucleocapsid exhibits a structure dominated largely alpha-helix irregular conformations. absence appreciable beta-structure P8 subunit suggests tertiary conformation lacking beta-barrel motif common to subunits most other viral capsids. addition, dodecahedral core also predominantly alpha-helical. results thus indicate alpha-helical for (P1) core, as well shell. Using difference spectroscopy, we demonstrate (P1, P2, P4 P7) interact extensively with packaged genome, further, conformational stability is reduced upon removal from core. Also, find significantly more thermostable than membrane envelope, which reported accompanying paper (Li et al., 1993). present suggest both architectural principles modes protein-RNA interaction differ fundamentally those icosahedral single-stranded viruses. Both circular dichroism genome an A-form marker bands signify presence only C3'-endo/anti nucleoside conformers. signature dsRNA, revealed spectrum discussed here model assessing base-pairing base-stacking interactions ribonucleoprotein assemblies.