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How Bacterial Flagella Flip Their Switch

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Science  16 Mar 2001:
Vol. 291, Issue 5511, pp. 2065-2067
DOI: 10.1126/science.291.5511.2065a

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Summary

Bacteria move by rotating their flagella, long, whiplike filaments that project from the cells. The flagellar filaments are helical, so in order to change direction, the bacterial cell generates a torque on the flagellar filaments that flips them into the opposite helix. But how does flagellin, the protein that makes up the filaments, achieve this dramatic structural shift? An x-ray crystallographic study of the protein described in this week's issue of Nature suggests that a sharp change within a very small "switch" region of flagellin is all that it takes to flip the left-handed flagellar helix into the right-handed form.