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  Topic: Evolution of prokaryote flagella, Links to discussions, webpages, refs< Next Oldest | Next Newest >  
niiicholas



Posts: 319
Joined: May 2002

(Permalink) Posted: Feb. 07 2003,01:31   

This would appear to be in support of the "the proton passes through the MotAB complex, and the resulting change of shape moves the FliG & C-ring"

Quote

At first sight, these two systems have little in common with the flagellar motor other than the use of a trans-membrane electrochemical gradient as an energy source. The bacterial flagellum is a complex macromolecular assemblage forming a multipartite structure composed of a long helical propeller, a flexible hook region and a rotary motor in the bacterial cytoplasmic membrane (for reviews, see Blair, 1995; DeRosier, 1998). The torque generation depends on the operation of a number of motors composed of the two proteins MotA and MotB. These proteins are believed to form the stator of the motor, arranged around the periphery of the flagellar basal body, which constitutes the rotor of the motor, and interacting specifically with the protein FliG, one of the subunits that form this basal body (Zhou et al., 1998a). The suggested mechanism is that protons traverse the membrane through a 'pore' formed by the MotA and MotB proteins. This 'pore' involves, in particular, a conserved aspartate residue of MotB (Asp-32) (Zhou et al., 1998b). Two conserved proline residues of MotA (Pro-173 and Pro-222) (Braun et al., 1999) are also particularly important in torque generation. On the basis of these studies, a model has been proposed (Braun et al., 1999) in which the first proline senses a conformational state and gates proton uptake by the aspartate residue from the periplasm. The proton uptake causes a change that either permits (via a Brownian ratchet) or drives rotation, a step involving the second proline residue. Finally, proton release into the cytoplasm restores the motor to its initial state.


Let's see if this graphic works:



Article:

Eric Cascales Roland Lloubès James N Sturgis Molecular Microbiology Volume 42 Issue 3 Page 795  - November 2001  
 
The TolQ-TolR proteins energize TolA and share homologies with the flagellar motor proteins MotA-MotB

  
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