Table 1. Data collection, image processing, and structure characteristics summary.

Map	Skeletal muscle α-actin	Cardiac muscle α-actin	β-actin	γ-actin
Data collection
Microscope	FEI Titan Krios G3i	FEI Titan Krios G3i	FEI Titan Krios G3i	FEI Titan Krios G3i
Voltage (kV)	300	300	300	300
Detector	Gatan K3	Gatan K3	Gatan K3	Gatan K3
Automation software	EPU	EPU	EPU	EPU
Energy filter slit width (eV)	20	20	20	20
Recording mode	Super-resolution	Super-resolution	Super-resolution	Super-resolution
Magnification (nominal)	81,000	81,000	81,000	81,000
Movie micrograph pixel size (Å)	0.891	0.891	0.891	0.891
Total Dose rate (e−/Å2)	65	60	50	65
Defocus range (µm)	–0.5 to –2.5	–0.5 to –2.5	–0.5 to –2.5	–0.5 to –2.5
Spherical aberration (mm)	0.01	0.01	0.01	0.01
Movies	2046	1444	1352	2952
Total extracted particles	261,195	657,300	279,120	1,249,379
Total # of refined particles	185,406	657,041	263,911	1,009,372
Reconstruction
EMDB code	EMD-27548	EMD-27549	EMD-27572	EMD-27565
Box size	350	256	256	256
Symmetry	helical	helical	C1	C1
Map sharpening B-factor (Å2)	–90	–149	–81	–201
Resolution (global) (Å)	3.37	3.07	2.99	3.38
Structure building and validation
PDB ID	8 DMX	8DMY	8DNH	8DNF
Model building	Coot	Coot	Coot	Coot
Refinement program	Phenix	Phenix	Phenix	Phenix
Refinement target	Real-space	Real-space	Real-space	Real-space
RMSD from ideal values
Bond length (Å)	0.02	0.02	0.04	0.03
Bond Angles (0)	0.493	0.494	0.761	0.711
Ramachandran favored (%)	97.61	96.68	96.21	96.20
Ramachandran allowed (%)	2.39	3.32	3.79	3.46
Ramachandran outliers (%)	0	0	0	0.34
MolProbity Score	1.42	1.42	1.72	1.72
Structures Characteristics
Species	Rabbit	Bovine	Human	Human
Amino acid resolved	4–375	2–375	1–374	1–374
PTMs resolved	H73	H73	D1/H72	E1/H72