+検索条件
-Structure paper
タイトル | Structural basis for DNA strand separation by a hexameric replicative helicase. |
---|---|
ジャーナル・号・ページ | Nucleic Acids Res, Vol. 43, Issue 17, Page 8551-8563, Year 2015 |
掲載日 | 2015年9月30日 |
著者 | Yuriy Chaban / Jonathan A Stead / Ksenia Ryzhenkova / Fiona Whelan / Ekaterina P Lamber / Alfred Antson / Cyril M Sanders / Elena V Orlova / |
PubMed 要旨 | Hexameric helicases are processive DNA unwinding machines but how they engage with a replication fork during unwinding is unknown. Using electron microscopy and single particle analysis we determined ...Hexameric helicases are processive DNA unwinding machines but how they engage with a replication fork during unwinding is unknown. Using electron microscopy and single particle analysis we determined structures of the intact hexameric helicase E1 from papillomavirus and two complexes of E1 bound to a DNA replication fork end-labelled with protein tags. By labelling a DNA replication fork with streptavidin (dsDNA end) and Fab (5' ssDNA) we located the positions of these labels on the helicase surface, showing that at least 10 bp of dsDNA enter the E1 helicase via a side tunnel. In the currently accepted 'steric exclusion' model for dsDNA unwinding, the active 3' ssDNA strand is pulled through a central tunnel of the helicase motor domain as the dsDNA strands are wedged apart outside the protein assembly. Our structural observations together with nuclease footprinting assays indicate otherwise: strand separation is taking place inside E1 in a chamber above the helicase domain and the 5' passive ssDNA strands exits the assembly through a separate tunnel opposite to the dsDNA entry point. Our data therefore suggest an alternative to the current general model for DNA unwinding by hexameric helicases. |
リンク | Nucleic Acids Res / PubMed:26240379 / PubMed Central |
手法 | EM (単粒子) |
解像度 | 18.0 - 23.0 Å |
構造データ | EMDB-3087, PDB-5a9k: EMDB-3088: EMDB-3089: EMDB-3090: EMDB-3091: |
化合物 | ChemComp-PO4: ChemComp-MG: ChemComp-HOH: |
由来 |
|
キーワード | HYDROLASE / DNA REPLICATION FORK |