potassium ion-transporting ATPase complex

Definition

Target type: cellularcomponent

Protein complex that carries out the reaction: ATP + H2O + K+(out) = ADP + phosphate + K+(in). It is a high affinity potassium uptake system. The E. coli complex consists of 4 proteins: KdpA is the potassium ion translocase, KdpB is the ATPase, and KdpC and KdpF seem to be involved in assembly and stabilization of the complex. [PMID:10608856, PMID:9858692]

The potassium ion-transporting ATPase complex, also known as the Na+/K+ ATPase or sodium-potassium pump, is a transmembrane protein complex crucial for maintaining cellular ion gradients and electrochemical potential. It is embedded in the plasma membrane, specifically the lipid bilayer, and its primary function is to transport sodium ions out of the cell and potassium ions into the cell, against their concentration gradients. This active transport process requires energy, which is supplied by the hydrolysis of ATP.

The complex is composed of two subunits: the α subunit and the β subunit. The α subunit is responsible for the catalytic activity and contains the binding sites for sodium, potassium, and ATP. It has ten transmembrane domains and is responsible for the actual ion transport. The β subunit is a glycoprotein that aids in the assembly and stability of the α subunit and may also regulate its activity. It has only one transmembrane domain and is located on the outer surface of the membrane.

The α subunit has two main conformations: E1 and E2. In the E1 conformation, the binding sites for sodium ions are accessible from the intracellular side, while in the E2 conformation, the binding sites for potassium ions are accessible from the extracellular side.

The overall process of ion transport can be summarized in the following steps:
1. Three sodium ions bind to the α subunit from the intracellular side, in the E1 conformation.
2. ATP binds to the α subunit and is hydrolyzed, releasing energy.
3. The conformational change to E2 occurs, exposing the sodium binding sites to the extracellular side and the potassium binding sites to the intracellular side.
4. Two potassium ions bind to the α subunit from the extracellular side.
5. The conformational change back to E1 occurs, exposing the potassium binding sites to the intracellular side and releasing the sodium ions to the extracellular side.
6. The potassium ions are released into the intracellular side, and the cycle repeats.

This process plays a vital role in maintaining the cell's membrane potential, which is essential for various cellular functions such as nerve impulse transmission, muscle contraction, and nutrient uptake.

The potassium ion-transporting ATPase complex is a highly regulated protein complex. Its activity can be modulated by various factors, including phosphorylation, changes in membrane potential, and interactions with other proteins. Dysfunction of this complex can lead to various diseases, including heart failure, hypertension, and neurological disorders.'
"

Proteins (3)

Compounds (19)