Information thermodynamics of cellular ion pumps

TL;DR

This paper applies bipartite stochastic thermodynamics to analyze the sodium-potassium pump, revealing information flow dynamics and Maxwell-demon behavior, especially during neuronal depolarization.

Contribution

It extends the thermodynamic analysis framework to ion-transporting proteins, uncovering information flow and Maxwell-demon phenomena in the sodium-potassium pump.

Findings

Information flow is comparable to other molecular machines.

Maxwell-demon behavior observed in ATP-consuming subsystem.

Information flow inverts during depolarization.

Abstract

The framework of bipartite stochastic thermodynamics is a powerful tool to analyze a composite system's internal thermodynamics. It has been used to study the components of different molecular machines such as ATP synthase. However, this approach has not yet been used to describe ion-transporting proteins despite their high-level functional similarity. Here we study the bipartite thermodynamics of the sodium-potassium pump in the nonequilibrium steady state. Using a physically intuitive partition between the ATP-consuming subsystem and the ion-transporting subsystem, we find considerable information flow comparable to other molecular machines, and Maxwell-demon behavior in the ATP-consuming subsystem. We vary ion concentrations and transmembrane voltage in a range including the neuronal action potential, and find that the information flow inverts during depolarization.