Polar Chemoreceptor Clustering by Coupled Trimers of Dimers

TL;DR

This paper presents a biophysical model explaining how bacterial chemotaxis receptors form large, stable polar clusters by balancing membrane elastic energy and receptor coupling, aligning with observed cellular behavior.

Contribution

The study introduces a coupled trimer of dimers model that predicts receptor cluster size based on membrane energy considerations, explaining polar localization.

Findings

Large polar clusters are favored at curved cell poles due to reduced curvature mismatch.

Lateral clusters are suppressed by membrane elastic energy penalties.

The model aligns with experimental observations of receptor clustering.

Abstract

Receptors of bacterial chemotaxis form clusters at the cell poles, where clusters act as "antennas" to amplify small changes in ligand concentration. Interestingly, chemoreceptors cluster at multiple length scales. At the smallest scale, receptors form dimers, which assemble into stable timers of dimers. At a large scale, trimers form large polar clusters composed of thousands of receptors. Although much is known about the signaling properties emerging from receptor clusters, it is unknown how receptors localize at the cell poles and what the cluster-size determining factors are. Here, we present a model of polar receptor clustering based on coupled trimers of dimers, where cluster size is determined as a minimum of the cluster-membrane free energy. This energy has contributions from the cluster-membrane elastic energy, penalizing large clusters due to their high intrinsic curvature, and receptor-receptor coupling favoring large clusters. We find that the reduced cluster-membrane curvature mismatch at the curved cell poles leads to large and robust polar clusters in line with experimental observation, while lateral clusters are efficiently suppressed.