Extreme Fuzzy Association of an Intrinsically Disordered Protein with Acidic Membranes

Many physiological and pathophysiological processes, including Mycobacterium tuberculosis (Mtb) cell division, may involve fuzzy membrane association by proteins via intrinsically disordered regions. The fuzziness is extreme when the conformation and pose of the bound protein and the composition of the proximal lipids are all highly dynamic. Here we tackled the challenge in characterizing the extreme fuzzy membrane association of the disordered, cytoplasmic N-terminal region (NT) of ChiZ, an Mtb divisome protein, by combining solution and solid-state NMR spectroscopy and molecular dynamics simulations. In a typical pose, NT is anchored to acidic membranes by Arg residues in the midsection. Competition for Arg interactions between lipids and acidic residues, all in the first half of NT, makes the second half more prominent in membrane association. This asymmetry is accentuated by membrane tethering of the downstream transmembrane helix. These insights into sequence-interaction relations may serve as a paradigm for understanding fuzzy membrane association.