2PKG: Structure Of A Complex Between The A Subunit Of Protein Phosphatase 2a And The Small T Antigen Of Sv40

The small t antigen (ST) of DNA tumor virus SV40 facilitates cellular transformation by disrupting the functions of protein phosphatase 2A (PP2A) through a poorly defined mechanism. The crystal structure of the core domain of SV40 ST bound to the scaffolding subunit of human PP2A reveals that the ST core domain has a novel zinc-binding fold and interacts with the conserved ridge of HEAT repeats 3-6, which overlaps with the binding site for the B' (also called PR61 or B56) regulatory subunit. ST has a lower binding affinity than B' for the PP2A core enzyme. Consequently, ST does not efficiently displace B' from PP2A holoenzymes in vitro. Notably, ST inhibits PP2A phosphatase activity through its N-terminal J domain. These findings suggest that ST may function mainly by inhibiting the phosphatase activity of the PP2A core enzyme, and to a lesser extent by modulating assembly of the PP2A holoenzymes.
PDB ID: 2PKGDownload
MMDB ID: 46595
PDB Deposition Date: 2007/4/17
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 3.3  Å
Source Organism:
Macaca mulatta polyomavirus 1
Similar Structures:
Biological Unit for 2PKG: dimeric; determined by author
Molecular Components in 2PKG
Label Count Molecule
Proteins (2 molecules)
Serine/threonine-protein Phosphatase 2A 65 KDA Regulatory Subunit a Alpha Isoform(Gene symbol: PPP2R1A)
Molecule annotation
Small T Antigen(Gene symbol: SV40gp7)
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB