Joined: May 2002
Regarding the cap:
February 2001 Volume 8 Number 2 pp 96 - 97
Putting a lid on it
Kelly T. Hughes & Phillip D. Aldridge
A cap at the tip of the bacterial flagellum uses a dynamic differential binding of individual subunits to allow the filament tip to grow, achieving control of assembly far from the point of protein translation.
Even though there is clear evidence that the flagellar filament can self assemble11, the cap of the flagellar filament serves to control its assembly12. The cap enables the filament to polymerize with high efficiency, so that every filament subunit that reaches the tip inserts into place. At the same time the bacterium continues to secrete other proteins through the filament that are presumed to simply pass by the cap and out into the extracellular medium. These include excess hook-filament junction subunits13, excess cap14 and a negative regulator of flagellin gene transcription15. This suggests that the cap acts as a gatekeeper that selectively retains filament subunits and may even play a role in helping them to fold into place.
11. Asakura, S. G. E. & Iino, T. J. Mol. Biol. 35, 227-236 (1968). | PubMed | ISI |
12. Homma, M. & Iino, T. J. Bacteriol. 162, 183-189 (1985). | PubMed | ISI |
13. Homma, M. & Iino, T. J. Bacteriol. 164, 1370-1372 (1985). | PubMed | ISI |
14. Hughes, K.T., Gillen, K.L., Semon, M.J. & Karlinsey, J.E. Science 262, 1277-1280 (1993). | PubMed | ISI |
15. Kutsukake, K. Mol. Gen. Genet. 243, 605-612 (1994). | PubMed | ISI |
Cool graphics mentioned in the article are online here:
Their density map: