Growth mechanism of the bacterial flagellar filament
The growth of bacterial flagellar filament requires a cap structure tightly attached to the distal end of the filament.
The cap is composed of HAP2 protein.
Maki et al.(1998) observed the cap-filament structure in electron microscope and revealed that a HAP2 pentamer is attached to the distal end of the filament.
To elucidate how the HAP2 subunits interact with the filament, we have been trying to analyze the structure of the cap-filament complex by electron cryomicroscopy.
We searched and found a condition under which the cap-filament complexes are stably formed.
They were examined in an electron microscope with a field emission gun operated at the specimen temperature of 4K.
Two dimensional alignment of the images was accomplished in x and y direction, separately using y and x axis projection of images, respectively.
The azimuthal angles were determined by the helical symmetry of the filament.
Then, the three dimensional structure of the complex was reconstructed by the back-projection method.
The structure obtained was shown here.
Model of the flagellar filament growth.