Flagellar rotation

Proton Flow Drives Bacterial Flagellar Rotation... 

Figure 34.32 Chemotaxis signaling pathway. Receptors in the plasma membrane initiate a signaling pathway leading to the phosphorylation of the CheY protein. Phosphorylated CheY binds to the flagellar motor and favors clockwise rotation. When an attractant binds to the receptor, this pathway is blocked, and counterclockwise flagellar rotation and, hence, smooth swimming result. When a repellant binds, the pathway is stimulated, leading to an increased concentration of phosphorylated CheY and, hence, more frequent clockwise rotation and tumbling.

Explain the role of proton-motive force in flagellar rotation. Present a model that explains the production of rotary motion from the effects of a proton gradient on the transmembrane flagellar motor. 

Describe the effect of phosphorylation of the che gene product CheY on flagellar rotation. 

Proton flow from the acidic solution can drive the bacterial flagellar rotation. 

The direction of proton flow would reverse when the direction of flagellar rotation reverses. Folloveing the converse of Figure 34.32, protons would need to flow from the inner half-channel to the MS ring, and then following clock-wise rotation to the outer half-channel. 

With the exception of some cyanobacteria that swim by rippling their outer membrane (7) Eubacteria and Archaea overcome the reciprocal motion problem by rotating helical flagellar filaments (8). Flagella almost certainly evolved independently but convergently in those two domains of life (9). Spirochetes hide the flagellar filaments between their inner and outer membranes, so that flagellar rotation causes the entire sinusoid or helical body to serve as the propeller (10). 

Silverman, M., and Simon, M. (1974) Flagellar rotation and the mechanism of bacterial motility. Nature 249, 73-74. 

Figure 4. A simplified scheme of the proton-motive force production by respiration and its use for flagellar rotation.

Salmonella of counterclockwise flagellar rotation. Consequently, runs are prolonged. clockwise rotation and pausing. Consequently, the cell tumbles and reorients more frequently. 407, 451]... 

S. melUoti Increased speed of flagellar rotation. Consequently, rnns are prolonged. Decreased speed of flagellar rotation. Consequently, the bundle of rotating flagella separates to individual filaments rotating at different speeds, and the cell turns. [675]... 

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