A symmetry mismatch at the site of RNA packaging in the polymerase complex of dsRNA bacteriophage φ6

被引:85
作者
de Haas, F
Paatero, AO
Mindich, L
Bamford, DH
Fuller, SD
机构
[1] European Mol Biol Lab, Struct Biol Programme, D-69117 Heidelberg, Germany
[2] Univ Helsinki, Dept Biosci, FIN-00014 Helsinki, Finland
[3] Univ Helsinki, Inst Biotechnol, FIN-00014 Helsinki, Finland
[4] Publ Hlth Res Inst City New York Inc, Dept Microbiol, New York, NY 10016 USA
[5] Univ Oxford, Div Struct Biol, Wellcome Trust Ctr Human Genet, Oxford OX3 7BN, England
关键词
cryo-electron microscopy; dsRNA viruses; packaging; symmetry mismatch; three-dimensional reconstruction;
D O I
10.1006/jmbi.1999.3260
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The polymerase complex of the enveloped double-stranded RNA (dsRNA) bacteriophage phi 6 fulfils a similar function to those of other dsRNA viruses such as Reoviridae. The phi 6 complex comprises protein P1, which forms the shell, and proteins P2, P4 and P7, which are involved in RNA synthesis and packaging. Icosahedral reconstructions from cryo-electron micrographs of recombinant polymerase particles revealed a clear dodecahedral shell and weaker satellites. Difference imaging demonstrated that these weak satellites were the sites of P4 and P2 within the complex. The structure determined by icosahedral reconstruction was used as an initial model in an iterative reconstruction technique to examine the departures from icosahedral symmetry. This approach showed that P4 and P2 contribute to structures at the 5-fold positions of the icosahedral P1 shell which lack 5-fold symmetry and appear in variable orientations. Reconstruction of isolated recombinant P4 showed that it was a hexamer with a size and shape matching the satellite. Symmetry mismatch between the satellites and the shell could play a role in RNA packaging akin to that of the portal vertex of dsDNA phages in DNA packaging. This is the first example of dsRNA virus in which the structure of the polymerase complex has been determined without the assumption of icosahedral symmetry. Our result with phi 6 illustrates the symmetry mismatch which may occur at the sites of RNA packaging in other dsRNA viruses such as members of the Reoviridae. (C) 1999 Academic Press.
引用
收藏
页码:357 / 372
页数:16
相关论文
共 79 条