Magic angle spinning NMR structure of human cofilin-2 assembled on actin filaments reveals isoform-specific conformation and binding mode

Abstract

Actin polymerization dynamics regulated by actin-binding proteins are essential for various cellular functions. The cofilin family of proteins are potent regulators of actin severing and filament disassembly. The structural basis for cofilin-isoform-specific severing activity is poorly understood as their high-resolution structures in complex with filamentous actin (F-actin) are lacking. Here, we present the atomic-resolution structure of the muscle-tissue-specific isoform, cofilin-2 (CFL2), assembled on ADP-F-actin, determined by magic-angle-spinning (MAS) NMR spectroscopy and data-guided molecular dynamics (MD) simulations. We observe an isoform-specific conformation for CFL2. This conformation is the result of a unique network of hydrogen bonding interactions within the α2 helix containing the non-conserved residue, Q26. Our results indicate F-site interactions that are specific between CFL2 and ADP-F-actin, revealing mechanistic insights into isoform-dependent F-actin disassembly.

Actin Bundles Dynamics and Architecture

“…Super-resolution fluorescence microscopy—in all its variants [ 384 ]—and ultrastructure expansion microscopy [ 385 ] are other fascinating tools that have added to—and will advance—our knowledge of cell assemblies. In addition to classical NMR and protein X-ray crystallography approaches, their modern modifications, such as magic angle spinning (solid-state) NMR (MAS NMR), have been successfully applied to characterize protein-decorated actin filaments [ 386 , 387 ], enabling the evaluation of protein dynamics. Adaptation of such structural methods to applications in cells [ 388 ] can aid in mapping the structures of proteins in their physiological context.…”

Performance efficient macromolecular mechanics via sub-nanometer shape based coarse graining

“…Next, we will describe parameter optimization via iterative Boltzmann inversion and discuss considerations for its deployment in high-granularity, sub-nanometer use-cases. We demonstrate the utility of this method via application to three unique protein structures, comprising two macromolecular biological assemblies: human cofilin-2 bound to actin filaments [37] and the full-scale HIV-1 conical capsid. Finally, we will provide guidance for configuring and performing SBCG simulations.…”

“…First, the aggregate sampling of the atomistic trajectory totals nearly half a microsecond, 480 ns; second, the corresponding SBCG trimer of dimers (Figure S4b), simulated throughout iterative refinement, provides ample opportunity for cross-validation throughout the process; and third, to preserve the dynamical behavior of the CA monomers (Figure S4c) in their assembly environment given the state-dependence of Boltzmann inversion. For actin and colifin-2, we utilized a similar approach, performing all-atom simulation of a single globular actin bound to one human cofilin-2 protein [37].…”

Performance efficient macromolecular mechanics via sub-nanometer shape based coarse graining

“…As mentioned before, we describe the derivation of a methodology for bond and angle parameter optimization via iterative Boltzmann inversion and discuss considerations for its deployment in high-granularity, sub-nanometer use-cases. We demonstrate the utility of the SBCG2 method via application to three unique protein structures, comprising two macromolecular biological assemblies: human cofilin-2 bound to actin filaments 44 and the full-scale HIV-1 conical capsid. In addition, we show the use of SBCG2 to probe the mechanoelastic properties of the HIV-1 capsid.…”