3DTP

Tarantula heavy meromyosin obtained by flexible docking to Tarantula muscle thick filament Cryo-EM 3D-MAP

ELECTRON MICROSCOPY

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Starting Model(s)

Initial Refinement Model(s)
Type	Source	Accession Code	Details
experimental model	PDB	1I84
experimental model	PDB	2FXM
experimental model	PDB	1B7T

Sample
Myosin thick filaments from Tarantula striated muscle

Specimen Preparation
Sample Aggregation State	FILAMENT
Vitrification Instrument
Cryogen Name
Sample Vitrification Details	Plunging in a liquid ethane. Blotting was performed from one side of the grid till a thin sample film on it using Whatman No 42 filter paper, then the grid was immediately plunged under gravity into liquid ethane cooled by liquid nitrogen. Grids were stored under liquid nitrogen.

3D Reconstruction
Reconstruction Method	HELICAL
Number of Particles	15504
Reported Resolution (Å)	20
Resolution Method
Other Details	three-dimensional single particle reconstruction was carried out by a modification of the ihrsr method, using spider. low-dose electron micrographs of 1008 frozen-hydrated thick filaments halves were digitized at 0.248 nm per pixel using a nikon super coolscan 8000 ed scanner. filaments were aligned with the bare zone at the top, to ensure correct polarity in subsequent steps. a total of 15,504 segments, each 62 nm long, with an overlap of 55.8 nm, and containing aprox. 40,000 unique pairs of interacting myosin heads went into the reconstruction. as an initial reference model we used the tarantula negatively stained 3d-map, which was axially rotated, axially shifted and also out of plane tilted up to plus-minus12deg. for projection matching, giving a total of 4,095 projections (13 tilted projections plus-minus 12 deg. every 2 deg., 45 reference rotated projections (0-90 deg., every 2 deg. rotation angle), and 7 image axial shifts of 2.2 nm. the resulting 3d-map combines about 10,700 out of 15,504 filament segments, a yield of 69 percent of included segments.
Refinement Type
Symmetry Type	HELICAL

Map-Model Fitting and Refinement
Id	1 (1I84, 2FXM, 1B7T)
Refinement Space	REAL
Refinement Protocol	FLEXIBLE FIT
Refinement Target	Constrained Molecular Dynamics
Overall B Value
Fitting Procedure
Details	METHOD--Flexible Fitting REFINEMENT PROTOCOL--Custom skeleton of 31 positional markers

Data Acquisition

Imaging Experiment	1
Date of Experiment	2001-09-19
Temperature (Kelvin)	88
Microscope Model	FEI/PHILIPS CM120T
Minimum Defocus (nm)	1950
Maximum Defocus (nm)	1950
Minimum Tilt Angle (degrees)
Maximum Tilt Angle (degrees)
Nominal CS	2
Imaging Mode	BRIGHT FIELD
Specimen Holder Model
Nominal Magnification	35000
Calibrated Magnification	35000
Source	LAB6
Acceleration Voltage (kV)	120
Imaging Details	Holey carbon grids Cryo preserved in Liquid ethane were observed in a Philips CM120 electron microscope under low dose conditions. Only filaments on thin carbon over holes were photographed

EM Software
Task	Software Package	Version
MODEL FITTING	Situs	3.2
MODEL FITTING	X-PLOR	3.851

Image Processing
CTF Correction Type	CTF Correction Details	Number of Particles Selected	Particle Selection Details
	no corrected