PDBsum entry 5avt

Hydrolase/transport protein

PDB id: 5avt

Contents

Protein chains

992 a.a.

268 a.a.

39 a.a.

Ligands

NAG-NAG

MF4

CLR

NAG

Metals

_TL ×3

_MG

__K ×2

Waters ×1

References listed in PDB file

Key reference

• Title: Sequential substitution of k(+) bound to na(+),K(+)-Atpase visualized by X-Ray crystallography.
• Authors: H.Ogawa, F.Cornelius, A.Hirata, C.Toyoshima.
• Ref.: Nat Commun, 2015, 6, 8004. [DOI no: 10.1038/ncomms9004]
• PubMed id: 26258479

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(+).