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Free keywords:
icosahedral reconstruction
symmetry mismatch
cryo-electron microscopy
virus
hexameric helicase
cystovirus
RNA packaging
double-stranded-rna
nucleoside triphosphatase p4
bacteriophage phi-6
cryoelectron-microscopy
3-dimensional reconstruction
dsrna
bacteriophage
symmetry mismatch
protein
resolution
DNA
Biochemistry & Molecular Biology
Biophysics
Cell Biology
Abstract:
Packaging of the Cystovirus phi 8 genome into the polymerase complex is catalysed by the hexameric P4 packaging motor. The motor is located at the fivefold vertices of the icosahedrally symmetric polymerase complex, and the symmetry mismatch between them may be critical for function. We have developed a novel image-processing approach for the analysis of symmetry-mismatched structures and applied it to cryo-electron microscopy images of P4 bound to the polymerase complex. This approach allowed us to solve the three-dimensional structure of the P4 in situ to 15-angstrom resolution. The C-terminal face of P4 was observed to interact with the polymerase complex, supporting the current view on RNA translocation. We suggest that the symmetry mismatch between the two components may facilitate the ring opening required for RNA loading prior to its translocation. (c) 2006 Elsevier Inc. All rights reserved.
