Structural transitions of F-actin upon ATP hydrolysis at near-atomic resolution revealed by cryo-EM

• Published in: Nature structural & molecular biology Vol. 25; no. 6; pp. 528 - 537
• Main Authors: Merino, Felipe, Pospich, Sabrina, Funk, Johanna, Wagner, Thorsten, Küllmer, Florian, Arndt, Hans-Dieter, Bieling, Peter, Raunser, Stefan
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.06.2018; Nature Publishing Group
• Subjects: 101/28; 4-Butyrolactone - analogs & derivatives; 4-Butyrolactone - metabolism; 631/45/612/1228; 631/535/1258/1259; Actin; Actins - chemistry; Actins - metabolism; Adenosine diphosphate; Adenosine Diphosphate - metabolism; Adenosine triphosphate; Adenosine Triphosphate - metabolism; Animals; ATP; ATP (Adenosine triphosphate); Binding proteins; Biochemistry; Biological Microscopy; Biomedical and Life Sciences; Catalysis; Composition; Cryoelectron Microscopy; Cytoplasmic filaments; Depsipeptides - metabolism; Filaments; Hydrolysis; Jasplakinolide; Life Sciences; Locks; Membrane Biology; Microfilament Proteins - metabolism; Muscle proteins; Muscle, Skeletal - metabolism; Muscles; Phosphates; Phosphates - metabolism; Physiological aspects; Polymerization; Protein Binding; Protein Conformation; Protein Structure; Protein-protein interactions; Proteins; Rabbits; Skeletal muscle; Structure; Toxins; Germany
• ISSN: 1545-9993; 1545-9985
• DOI: 10.1038/s41594-018-0074-0

The function of actin is coupled to the nucleotide bound to its active site. ATP hydrolysis is activated during polymerization; a delay between hydrolysis and inorganic phosphate (P i ) release results in a gradient of ATP, ADP–P i and ADP along actin filaments (F-actin). Actin-binding proteins can recognize F-actin’s nucleotide state, using it as a local ‘age’ tag. The underlying mechanism is complex and poorly understood. Here we report six high-resolution cryo-EM structures of F-actin from rabbit skeletal muscle in different nucleotide states. The structures reveal that actin polymerization repositions the proposed catalytic base, His161, closer to the γ-phosphate. Nucleotide hydrolysis and P i release modulate the conformational ensemble at the periphery of the filament, thus resulting in open and closed states, which can be sensed by coronin-1B. The drug-like toxin jasplakinolide locks F-actin in an open state. Our results demonstrate in detail how ATP hydrolysis links to F-actin’s conformational dynamics and protein interaction. Cryo-EM structures of F-actin captured in different nucleotide states, by using nucleotide analogs or small molecules, reveal different conformational states linked to ATP hydrolysis.