PDBsum entry: 2iae

Hydrolase/hydrolase inhibitor

PDB id: 2iae

Contents

Protein chains

583 a.a. *

376 a.a. *

306 a.a. *

291 a.a. *

Ligands

DAL-LEU-ACB-ARG-1ZN-FGA-DAM ×2

Metals

_MN ×4

* Residue conservation analysis

PDB id:

2iae

Name:

Hydrolase/hydrolase inhibitor

Title:

Crystal structure of a protein phosphatase 2a (pp2a) holoenz

Structure:

Serine/threonine-protein phosphatase 2a 65 kda re subunit a alpha isoform. Chain: a, d. Fragment: aalpha subunit. Synonym: pp2a, subunit a, pr65-alpha isoform, pp2a, subunit alpha isoform. Engineered: yes. Serine/threonine-protein phosphatase 2a 56 kda re subunit gamma isoform.

Source:

Mus musculus. House mouse. Organism_taxid: 10090. Gene: ppp2r1a. Expressed in: escherichia coli. Expression_system_taxid: 562. Homo sapiens. Human. Organism_taxid: 9606.

Resolution:

3.50Å R-factor: 0.260 R-free: 0.316

Authors:

U.S.Cho,W.Xu

Key ref:

U.S.Cho and W.Xu (2007). Crystal structure of a protein phosphatase 2A heterotrimeric holoenzyme. Nature, 445, 53-57. PubMed id: 17086192 DOI: 10.1038/nature05351

Date:

07-Sep-06 Release date: 26-Dec-06

Protein chains

Q76MZ3  (2AAA_MOUSE) -  Serine/threonine-protein phosphatase 2A 65 kDa regulatory subunit A alpha isoform

Seq: 589 a.a.

Struc: 583 a.a.

Protein chains

Q13362  (2A5G_HUMAN) -  Serine/threonine-protein phosphatase 2A 56 kDa regulatory subunit gamma isoform

Seq: 524 a.a.

Struc: 376 a.a.

Protein chain

P67775  (PP2AA_HUMAN) -  Serine/threonine-protein phosphatase 2A catalytic subunit alpha isoform

Seq: 309 a.a.

Struc: 306 a.a.*

Protein chain

P67775  (PP2AA_HUMAN) -  Serine/threonine-protein phosphatase 2A catalytic subunit alpha isoform

Seq: 309 a.a.

Struc: 291 a.a.*

* PDB and UniProt seqs differ at 3 residue positions (black crosses)

Enzyme reactions

• Enzyme class: Chains C, F: E.C.3.1.3.16 - Phosphoprotein phosphatase.
• Reaction: A phosphoprotein + H₂O = a protein + phosphate

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

 Gene Ontology (GO) functional annotation 

• Cellular component: membrane (13 terms)
• Biological process: positive regulation of protein serine/threonine kinase activity (30 terms)
• Biochemical function: binding (11 terms)

Added reference

DOI no: 10.1038/nature05351

Nature 445:53-57 (2007)

PubMed id: 17086192

Crystal structure of a protein phosphatase 2A heterotrimeric holoenzyme.

U.S.Cho, W.Xu.

ABSTRACT

Protein phosphatase 2A (PP2A) is a principal Ser/Thr phosphatase, the deregulation of which is associated with multiple human cancers, Alzheimer's disease and increased susceptibility to pathogen infections. How PP2A is structurally organized and functionally regulated remains unclear. Here we report the crystal structure of an AB'C heterotrimeric PP2A holoenzyme. The structure reveals that the HEAT repeats of the scaffold A subunit form a horseshoe-shaped fold, holding the catalytic C and regulatory B' subunits together on the same side. The regulatory B' subunit forms pseudo-HEAT repeats and interacts with the C subunit near the active site, thereby defining substrate specificity. The methylated carboxy-terminal tail of the C subunit interacts with a highly negatively charged region at the interface between A and B' subunits, suggesting that the C-terminal carboxyl methylation of the C subunit promotes B' subunit recruitment by neutralizing charge repulsion. Together, our structural results establish a crucial foundation for understanding PP2A assembly, substrate recruitment and regulation.

Selected figure(s)

Figure 2.
Figure 2: Structures of the scaffold A subunit, the catalytic C alpha-subunit and the A–C interface. a, Structure comparison of the A subunit alone (grey) and in the trimeric complex (blue), with front and top views. In the complex structure, the A subunit intra-repeat loops, which are responsible for B and C subunit binding, form a circle narrower than that formed by inter-repeat loops. Conformational changes of repeats 11–15 are mostly derived from the interface change between repeats 12–13. b, A structure superposition of the PP2A C subunit (orange), PP1 (yellow) and PP2B catalytic domain (grey). c, A surface representation of the C subunit with microcystin-LR (shown in stick representation). d, Interface of the A (blue) and C subunits (orange). Red boxes represent positions of genetic mutations found in melanoma cancer (R418W)^27 and colon adenocarcinoma (V545A in PP2A A )^29; the red underline indicates the position of a previously identified mutant that interrupts the A–C interaction (K416E)^28. Dashed lines indicate hydrogen bonds.

Figure 5.
Figure 5: Interactions between the methylated C-terminal tail of the catalytic C alpha-subunit and the A–B interface. a, Overall position of the C-terminal tail of the C subunit in the trimeric complex and a stereo view of detailed interactions. The red box indicates the position of genetic mutations E64D and E64G found in lung and breast cancer patients, respectively. b, The methylated C-terminal tail of the C subunit is positioned in the middle of four negatively charged residues of the A subunit (in red). c, A schematic model of the regulatory mechanism of C-terminal tail methylation in formation of the trimeric A–B56–C complex. The affinity between the B56 subunit and the AC core enzyme is too low to form a stable complex, and the unmethylated C-terminal tail of the C subunit cannot settle down on the A–B interface due to the charge repulsion between the carboxyl group of C-terminal Leu 309 and the negatively charged surface on the A subunit near the proposed binding area. When the C-terminal tail of the C subunit is methylated by phosphatase methyltransferase (PMT), charge repulsion is neutralized and the methylated C-terminal tail can settle down on the A–B interface. This allows for the recruitment of B56 to form a stable AB'C heterotrimeric complex.

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nature (2007, 445, 53-57) copyright 2007.

Figures were selected by the author.