journal menu
![[Figure 4]](id5005fig4mag.jpg)
|
|
Figure 4
Dynamic in vitro-polymerized MTs visualized by cryo-electron tomography. (a) Top, 0° tilt image (motion-corrected movie sum; ∼2 e− Å−2 total dose) from a tilt series, showing a typical field of MTs that includes views of the MT lattice (red arrowheads, including the moiré pattern) and MT ends (pink arrows), together with 10 nm gold fiducial markers. Bottom, 8 nm section through the three-dimensional tomographic reconstruction of the same sample, showing the appearance of sections through the MT wall (red arrowhead) in which individual PFs are visible, the MT lumen (orange arrowheads), MT ends (pink arrow), tubulin PF spirals (blue arrows) and unpolymerized tubulin (yellow arrows). (b) Exemplar 0° tilt MT image (left) and Fourier filtered image (right) showing the moiré patterns characteristic of (i) a 14PF MT and (ii) a 13PF MT. Because the 14PF MT is not sitting perfectly flat within the plane of the vitreous ice, the arrowhead shape within the moiré pattern that might be used to indicate MT polarity is not visible, but its polarity was determined using the change in appearance of the moiré pattern with the tilt angle. Because the PFs lie parallel to the MT axis in the architecture of the 13PF MT, the moiré pattern does not vary along the MT length and its polarity cannot be determined using this approach. (c) Rotational averaging analysis of 8 nm thick transverse sections from the tomographic reconstruction supports the moiré-pattern-based assignment of PF architecture for these MTs. (d) Transverse section (top) and segmented and surface-rendered view (bottom) through the same tomogram, showing the distribution of the MTs (red) in the vitreous ice layer, the tendency of background protein (tubulin, yellow) to lie more at the air–water interface of the sample and the tendency of the tubulin spirals (blue) to lie horizontally at the centre of the ice layer. |
![[Figure 4]](id5005fig4.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
access
