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| Title | Six molecules of SV40 large T antigen assemble in a propeller-shaped particle around a channel. |
|---|---|
| Journal, issue, pages | J Mol Biol, Vol. 268, Issue 1, Page 15-20, Year 1997 |
| Publish date | Apr 25, 1997 |
 Authors | M C San Martín / C Gruss / J M Carazo /  |
| PubMed Abstract | The large T antigen of simian virus 40 (SV40) is a multifunctional regulatory protein, responsible for both the control of viral infection and the required alterations of cellular processes. T ...The large T antigen of simian virus 40 (SV40) is a multifunctional regulatory protein, responsible for both the control of viral infection and the required alterations of cellular processes. T antigen is the only viral protein required for viral DNA replication. It binds specifically to the viral origin and as a helicase unwinds the SV40 DNA bidirectionally. The functional complex is a double hexameric oligomer. In the absence of DNA, but in the presence of ATP or a non-hydrolyzable analog, T antigen assembles into hexamers, which are active as a helicase when a partially single-stranded (3') entry site exists on the substrate. We have used negative staining electron microscopy, single particle image processing and three-dimensional reconstruction with a new algebraic reconstruction techniques (ART) algorithm to study the structure of these hexameric particles in the presence of different nucleotide cofactors (ATP, ADP, and the non-hydrolyzable analogs ATPgammaS and AMP-PNP). In every case a strong 6-fold structure was found, with the six density maxima arranged in a ring-like particle around a channel, and a well-defined vorticity. Because these structural features have recently been found in other prokaryotic helicases, they seem to be strongly related to the activity of the protein, which suggests a general functional model conserved through evolution. |
 External links | J Mol Biol / PubMed:9149137 |
| Methods | EM (single particle) |
| Resolution | 29.0 Å |
| Structure data |  EMDB-1024: |
| Source |
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Simian virus 40