5A9K

Structural basis for DNA strand separation by a hexameric replicative helicase

Summary for 5A9K

• Entry DOI: 10.2210/pdb5a9k/pdb
• Related: 5A9L 5A9M 5A9N 5A9O
• EMDB information: 3087
• Descriptor: REPLICATION PROTEIN E1, PHOSPHATE ION, MAGNESIUM ION, ... (4 entities in total)
• Functional Keywords: hydrolase, dna replication fork
• Biological source: BOVINE PAPILLOMAVIRUS
• Cellular location: Host nucleus : P03116
• Total number of polymer chains: 6
• Total formula weight: 208797.75

Authors

Chaban, Y.,Stead, J.A.,Ryzhenkova, K.,Whelan, F.,Lamber, K.,Antson, F.,Sanders, C.M.,Orlova, E.V. (deposition date: 2015-07-21, release date: 2015-08-26, Last modification date: 2024-05-08)

Primary citation

Chaban, Y.,Stead, J.A.,Ryzhenkova, K.,Whelan, F.,Lamber, K.,Antson, A.,Sanders, C.M.,Orlova, E.V.
Structural Basis for DNA Strand Separation by a Hexameric Replicative Helicase.
Nucleic Acids Res., 43:8551-, 2015

PubMed Abstract: 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.

PubMed: 26240379
DOI: 10.1093/NAR/GKV778

Experimental method

ELECTRON MICROSCOPY (19 Å)