4XW4: X-ray Structure Of Pkac With Amppnp, Sp20, Calcium Ions

To study the catalytic mechanism of phosphorylation catalyzed by cAMP-dependent protein kinase (PKA) a structure of the enzyme-substrate complex representing the Michaelis complex is of specific interest as it can shed light on the structure of the transition state. However, all previous crystal structures of the Michaelis complex mimics of the PKA catalytic subunit (PKAc) were obtained with either peptide inhibitors or ATP analogs. Here we utilized Ca(2+) ions and sulfur in place of the nucleophilic oxygen in a 20-residue pseudo-substrate peptide (CP20) and ATP to produce a close mimic of the Michaelis complex. In the ternary reactant complex, the thiol group of Cys-21 of the peptide is facing Asp-166 and the sulfur atom is positioned for an in-line phosphoryl transfer. Replacement of Ca(2+) cations with Mg(2+) ions resulted in a complex with trapped products of ATP hydrolysis: phosphate ion and ADP. The present structural results in combination with the previously reported structures of the transition state mimic and phosphorylated product complexes complete the snapshots of the phosphoryl transfer reaction by PKAc, providing us with the most thorough picture of the catalytic mechanism to date.
PDB ID: 4XW4Download
MMDB ID: 129115
PDB Deposition Date: 2015/1/28
Updated in MMDB: 2015/07
Experimental Method:
x-ray diffraction
Resolution: 1.82  Å
Source Organism:
Mus musculus
Similar Structures:
Biological Unit for 4XW4: dimeric; determined by author and by software (PISA)
Molecular Components in 4XW4
Label Count Molecule
Proteins (2 molecules)
Camp-dependent Protein Kinase Catalytic Subunit Alpha(Gene symbol: Prkaca)
Molecule annotation
Camp-dependent Protein Kinase Inhibitor Alpha
Molecule annotation
Chemicals (3 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB