Two-Dimensional Crowding Uncovers a Hidden Conformation of α-Synuclein.
The intrinsically disordered protein (IDP), α-synuclein (αS), is well-known for phospholipid membrane binding-coupled folding into tunable helical conformers. Here, using single-molecule experiments in conjunction with ensemble assays and a theoretical model, we present a unique case demonstrating that the interaction-folding landscape of αS can be tuned by two-dimensional (2D) crowding through simultaneous binding of a second protein on the bilayer surface. Unexpectedly, the experimental data show a clear deviation from a simple competitive inhibition model, but are consistent with a bimodal inhibition mechanism wherein membrane binding of a second protein (a membrane interacting chaperone, Hsp27, in this case) differentially inhibits two distinct modules of αS-membrane interaction. As a consequence, αS molecules are forced to access a hidden conformational state on the phospholipid bilayer in which only the higher-affinity module remains membrane-bound. Our results demonstrate that macromolecular crowding in two dimensions can play a significant role in shaping the conformational landscape of membrane-binding IDPs with multiple binding modes.
Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Priya R
PR
Banerjee
Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Mahdi Muhammad
MM
Moosa
Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Ashok A
AA
Deniz
D011487:Protein Conformation; D051844:alpha-Synuclein / Q000737:chemistry*
D051844:alpha-Synuclein
Hsp27; biophysics; molecular crowding; protein folding; single-molecule studies