5AVT: Kinetics By X-ray Crystallography: Tl+-substitution Of Bound K+ In The E2.mgf42-.2k+ Crystal After 5 Min

Citation:
Abstract
Na(+),K(+)-ATPase transfers three Na(+) from the cytoplasm into the extracellular medium and two K(+) in the opposite direction per ATP hydrolysed. The binding and release of Na(+) and K(+) are all thought to occur sequentially. Here we demonstrate by X-ray crystallography of the ATPase in E2.MgF4(2-).2K(+), a state analogous to E2.Pi.2K(+), combined with isotopic measurements, that the substitution of the two K(+) with congeners in the extracellular medium indeed occurs at different rates, substantially faster at site II. An analysis of thermal movements of protein atoms in the crystal shows that the M3-M4E helix pair opens and closes the ion pathway leading to the extracellular medium, allowing K(+) at site II to be substituted first. Taken together, these results indicate that site I K(+) is the first cation to bind to the empty cation-binding sites after releasing three Na(+).
PDB ID: 5AVTDownload
MMDB ID: 132289
PDB Deposition Date: 2015/7/1
Updated in MMDB: 2015/09
Experimental Method:
x-ray diffraction
Resolution: 2.9  Å
Source Organism:
Similar Structures:
Biological Unit for 5AVT: trimeric; determined by author and by software (PISA)
Molecular Components in 5AVT
Label Count Molecule
Proteins (3 molecules)
1
NA, K-atpase Alpha Subunit
Molecule annotation
1
Na+,k+-atpase Beta Subunit
Molecule annotation
1
Phospholemman-like Protein
Molecule annotation
Chemicals (11 molecules)
1
1
2
1
3
2
4
3
5
1
6
3
* Click molecule labels to explore molecular sequence information.

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