Effect of protein sequence, subunit composition and phosphorylation on neurofilament brush structure and morphology

Neurofilaments (NFs) are multi-subunit intermediate filaments whose intrinsically disordered brush regions are thought to dictate the structure, behavior and stability of axons. However, a fundamental understanding on the sequence-structure relationship of NF subunits as well as the effect of subunit composition on neurofilament brush morphology is lacking. We apply a self-consistent field theory paired with a robust experimental platform to study single-component, binary, and ternary neurofilament-derived brushes under a wide range of ionic conditions. The theoretical predictions on overall brush height are in good agreement with experimental measurements using atomic force microscopy. The theory is able to provide the role of each subunit amino acid sequence on the underlying protein conformations and overall morphology of the NF brushes. The theory is extended to compare the effect of species on neurofilament-medium (NFM) brushes, finding strikingly similar morphologies in rat, mouse, bovine, and human NFM brushes upon phosphorylation.