Self-Assembly of Bacterial Flagella
Bacteria swim in viscous liquid environments by rotating helical propellers
called flagella.
The bacterial flagellum is a nanomachine made of about 25
different proteins, each of them in multiple copies ranging from a few
to tens of thousands. It is constructed by self-assembly of these large
numbers of proteins, each into a different part that exerts a different
function, such as a rotary motor, bushing, drive shaft, rotation-switch
regulator, universal joint, helical propeller, and rotary promoter for
self-assembly.
Flagellar proteins are synthesized within the cell body
and transported through a long, narrow central channel in the flagellum
to its distal (outer) end, where they self-assemble to construct complex
nano-scale structures efficiently, with the help of the flagellar cap
as the assembly promoter. The rotary motor, with a diameter of only
30 to 40 nm, drives the rotation of the flagellum at around 300 Hz,
at a power level of 10-16 W with energy conversion efficiency
close to 100 %.
The structural designs and functional mechanisms to be revealed
in the complex machinery of the bacterial flagellum could provide many
novel technologies that would become a basis for future nanotechnology,
from which we should be able to find many useful applications.
(Thanks to Dr. Keiichi Namba for the caption and figure.)
