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Unformatted text preview: Microbial Physio Lecture 11: Bacterial Flagellum continued October 18, 2010 Motor: a. Stator: MotA/ MotB protein is the ion selector (H + or Na + are the 2 possible ions that can flow through this motor) a. The 2 types of proteinMotA and Mot B only differ by a few amino acids that determine their specificity for the specific ions b. MotA/B is a complex that serves as an ion selector it is the movement of the H + and Na + ions that provides the energy i. The ions move from the outside insideit is more acidic outside than inside and ions therefore flow inside to the cell b. Rotor: The flagellum ( FliF, G, M, N) a. The C-terminal domain of FliG (which is highly charged) interacts w/ MotAB complex, and it does so via electrostatic interactions( to allow transfer of energy) to produce the torque to rotate the flagellum i. We know that it interacts w/ the MotAB complex via electrostatic interactions because if you change the charged resides in the C-terminal domain of FliGyou interfere w/ the electrostatic interactions, and the motor will still fxn in the sense that H + or Na + ions will still flow through the motor, but you wont get flagellar rotation ii. FliG/M/N dictates which way the flagellar rotates iii. CheY-Phosphate talks to FliM at the basal region of the flagella and signals for tumbling of the bacterium b. It was thought for a while that FliF to be a chaperone protein that put the complex together, but it seems that while this may be a chaperone protein, the F protein is incorporated into the complex many chaperones proteins become structural elements that they are involved in constructing The 4 proteins (FliFGMN) can be mutated , and when theyre mutated, they give rise to 3 distinct types of phenotypes : 1. Flagellum- 1. Flagellum cant be assembled 2. this makes sense because FliFGMN are part of the basal body of the flagellum, so if theyre deleted, then you would expect to have a fla- phenotype ( flagellum- ) no flagellum made 2. Motility- 1. Get this phenotype when KO or alter MotA/B 2. This makes sense because if you dont assemble this one part of the basal body of the flagellum correctly, or you KO some of the + charged residue in FliG protein in the C-terminal domain, then you dont get proper interaction w/ MotAB, and consequently, even though the flagellum is synthesized and assembled correctly, it cant rotate, because FliG doesnt have the electrostatic interactions w/ MotAB 3. Chemotaxis- 1. they can assemble the flagellum correctly 2. they can link the flagellum to the rotor and therefore can rotate 3. but they cant be directed towards any of the normal chemoattractants/chemorepellents 4. this also makes sense because CheY phosphate has to go and bind to the element at the tip of the basal region on the inside ( inside the cytoplasm) in order to initiate a change in rotational direction i. so under normal conditions, counter clockwise is the normal rotation( default) that tells it to swim straight in forward...
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This note was uploaded on 01/09/2011 for the course BIMM 130 taught by Professor Saier during the Fall '10 term at UCSD.
- Fall '10