TWO HEAVY MEROMYOSIN INTERACTING-HEADS MOTIFS FLEXIBLE DOCKED INTO TARANTULA THICK FILAMENT 3D-MAP ALLOWS IN DEPTH STUDY OF INTRA- AND INTERMOLECULAR INTERACTIONS
ELECTRON MICROSCOPY
Sample
Myosin filaments from Tarantula striated muscle
Sample Components
MYOSIN II
Specimen Preparation
Sample Aggregation State
FILAMENT
Vitrification Instrument
HOMEMADE PLUNGER
Cryogen Name
ETHANE
Sample Vitrification Details
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 ...
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
Reported Resolution (Å)
20
Resolution Method
FSC 0.5 CUT-OFF
Other Details
Three-dimensional single particle reconstruction was carried out by a modification of the IHRSR method, using SPIDER. Low-dose electron micrographs of ...
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 ere 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-minus12deg. every 2deg., 45 reference rotated projections (0-90 degrees, 2deg. 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. There are 4 helices of myosin heads, rotated 30 degrees, every 145 Angstroms. The filament segments were selected based on visual judgement of good helical order.
Refinement Type
Symmetry Type
HELICAL
Axial Symmetry
C4
Axial Rise
100
Angular Rotation
30
Map-Model Fitting and Refinement
Id
1 (3DTP)
Refinement Space
REAL
Refinement Protocol
FLEXIBLE FIT
Refinement Target
Correlation
Overall B Value
Fitting Procedure
Details
METHOD--FLEXIBLE FITTING DETAILS--Protocol- Flexible Fitting. The flexible
docking procedure is based on a connected (motion capture) network of
ide ...
METHOD--FLEXIBLE FITTING DETAILS--Protocol- Flexible Fitting. The flexible
docking procedure is based on a connected (motion capture) network of
identified features within the atomic model. The atomic model is allowed to
move according to displacements tracked by 31 control points defined by the
network, in order to find the best match to the cryo-EM map
