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Atoms of Apoferritin
At a miraculous 1.22 Å resolution, the electron microscopy map of
mouse apoferritin (right,
EMDB 11638)
can be mistaken for an atomic model (left,
PDB 7a4m),
with each atom standing out.
The map from Nakane et al. (2020 Nature 587:152-156)
shows glimpses of the lightest atoms, hydrogen, directly revealing the
hydrogen-bonding network.
Ferritin stores iron, as many as 4500 ions (Fe3+), as crystallites
within its shell of 24 proteins. Apoferritin, ferritin without its iron cargo,
has rock-like stability, making it ideal for divining the limits of
electron microscope resolution.
The images were made with UCSF ChimeraX,
using ambient-occlusion lighting,
coloring to delineate trimeric subunits within the dodecahedral shell,
and curved helix tubes.
Best wishes for a happy and healthy 2021!
Conrad, Greg, Elaine, Tristan, Tom, Scooter, Eric and Tom
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