Self-consistent field theory for the interactions between keratin intermediate filaments

TL;DR

This paper presents a self-consistent field theory model for keratin filament interactions, highlighting how terminal domain properties and medium composition influence filament attraction and tissue elasticity.

Contribution

It introduces a detailed theoretical model linking keratin terminal domain interactions to filament attraction, incorporating electrostatics and bridging effects near charge compensation.

Findings

Terminal chains mediate weak attraction between keratin surfaces.

Attraction depends on charge compensation and medium composition.

Results align with experimental observations of keratin interactions.

Abstract

We have developed a model for the interactions between keratin intermediate filaments based on self-consistent field theory. The intermediate filaments are represented by charged surfaces, and the disordered terminal domains of the keratins are represented by charged heteropolymers grafted to these surfaces. We estimate the system is close to a charge compensation point where the heteropolymer grafting density is matched to the surface charge density. Using a protein model with amino acid resolution for the terminal domains, we find that the terminal chains can mediate a weak attraction between the keratin surfaces. The origin of the attraction is a combination of bridging and electrostatics. The attraction disappears when the system moves away from the charge compensation point, or when excess small ions and/or NMF-representing free amino acids are added. These results are in concordance with experimental observations, and support the idea that the interaction between keratin filaments, and ultimately in part the elastic properties of the keratin-containing tissue, is controlled by a combination of the physico-chemical properties of the disordered terminal domains and the composition of the medium in the inter-filament region.