Key resources table.

Reagent type (species) or resource	Designation	Source or reference	Identifiers	Additional information
Strain, strain background (P. pastoris)	P. pastoris transformants	https://journals.biologists.com/jcs/article/131/8/jcs213827/57192/Rapid-production-of-pure-recombinant-actin		Hatano et al., 2018; P. pastoris transformants used to prepare recombinant b-actin (H. sapiens) and g-actin (H. sapiens)
Biological sample (O. cuniculus)	Skeletal muscle	Pel-Freez	41995	Muscle acetone powder used for the preparation of native skeletal muscle a-actin
Biological sample (B. taurus)	heart	Local butcher		Left ventricle used for the preparation of native cardiac muscle a-actin
Other (O. cuniculus)	skeletal muscle a-actin	This paper	UniProt ID: P68135	Peptide, protein reagent, prepared from muscle acetone powder
Other (B. taurus)	cardiac muscle a-actin	This paper	UniProt ID: Q3ZC07	Peptide, protein reagent, prepared from bovine heart
Peptide, recombinant protein (H. sapiens)	b-actin	This paper	UniProt ID: P60709	Prepared from P. pastoris transformants
Peptide, recombinant protein (H. sapiens)	g-actin	This paper	UniProt ID: P63261	Prepared from P. pastoris transformants
Other	Amicon 30 kDa MWCO centrifugal filters	Millipore Sigma	UFC903008	Protein concentrators
Other	C-flat Au 1.2/1.3 grids	Electron Microscopy Sciences	CF313-50-Au	Electron microscopy grids
Software, algorithm	EPU	Thermo Fisher Scientific		Software for cryo-EM data acquisition
Software, algorithm	cryoSPARC	https://doi.org/10.1038/nmeth.4169		Punjani et al., 2017
Software, algorithm	MotionCor2	https://doi.org/10.1038/nmeth.4193		Zheng et al., 2017
Software, algorithm	Coot	https://doi.org/10.1107/S0907444910007493		Emsley et al., 2010
Software, algorithm	PHENIX	https://doi.org/10.1107/S0907444909052925		Adams et al., 2010
Software, algorithm	Chimera	https://doi.org/10.1002/jcc.20084		Pettersen et al., 2004
Software, algorithm	MolProbity	https://doi.org/10.1002/pro.3330		Williams et al., 2018