Regulation of Switching Frequency and Bias of the Bacterial Flagellar Motor by CheY and Fumarate
AUTOR(ES)
Montrone, Marco
FONTE
American Society for Microbiology
RESUMO
The effect of CheY and fumarate on switching frequency and rotational bias of the bacterial flagellar motor was analyzed by computer-aided tracking of tethered Escherichia coli. Plots of cells overexpressing CheY in a gutted background showed a bell-shaped correlation curve of switching frequency and bias centering at about 50% clockwise rotation. Gutted cells (i.e., with cheA to cheZ deleted) with a low CheY level but a high cytoplasmic fumarate concentration displayed the same correlation of switching frequency and bias as cells overexpressing CheY at the wild-type fumarate level. Hence, a high fumarate level can phenotypically mimic CheY overexpression by simultaneously changing the switching frequency and the bias. A linear correlation of cytoplasmic fumarate concentration and clockwise rotation bias was found and predicts exclusively counterclockwise rotation without switching when fumarate is absent. This suggests that (i) fumarate is essential for clockwise rotation in vivo and (ii) any metabolically induced fluctuation of its cytoplasmic concentration will result in a transient change in bias and switching probability. A high fumarate level resulted in a dose-response curve linking bias and cytoplasmic CheY concentration that was offset but with a slope similar to that for a low fumarate level. It is concluded that fumarate and CheY act additively presumably at different reaction steps in the conformational transition of the switch complex from counterclockwise to clockwise motor rotation.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=107292Documentos Relacionados
- Roles of cheY and cheZ gene products in controlling flagellar rotation in bacterial chemotaxis of Escherichia coli.
- Restoration of flagellar clockwise rotation in bacterial envelopes by insertion of the chemotaxis protein CheY.
- A chemotactic signaling surface on CheY defined by suppressors of flagellar switch mutations.
- Overexpression and sequence of the Escherichia coli cheY gene and biochemical activities of the CheY protein.
- CheZ Has No Effect on Flagellar Motors Activated by CheY13DK106YW