Microbial Physiology notes lec7 10-8-10

Microbial Physiology notes lec7 10-8-10 - Microbial...

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Microbial Physiology notes Lecture 7: October 8, 2010 Cell Polarity continued C. Chemosensory apparatus in E. coli R’= an MCP (Tar, Tsr, Trg, Tap, Aer) R’: W: A= 28:6:4 R’ and W (and maybe A) are needed for polar localization. Why? How? -In cytoplasmic membrane there is a receptor R’ = MCP= methyl accepting Chemotaxis protein receptor -binds solids (attractants/repellents) on the outside of the cytoplasmic membrane in the extracellular space and it transmits a signal to the cytoplasmic surface of itself signal indicates what the conformation of interacting protein will be -interacting proteins are called che W and che A -che W is a transmission protein that responds to the binding of MCP the MCP binding to substrates such as che W has a big impact on MCP conformation which then affects the ability of it to undergo transmission of information to the inside of the cell -che= Chemotaxis -Chemotaxis is + when there is movement in the direction of a higher [ ] of the chemical in question -Chemotaxis is – when there is movement in the opposite direction of a higher [ ] of the chemical in question -che W and A interact directly w/ MCP and they control the oligomeric state of R’ protein -normally when W and A protein are made they’re just made as monomers that then clump together and always at the pole of the cell and clumping is essential because the clumping demonstrates both negative and positive cooperativity as seen in proteins like hemoglobin, and that allows the bacteria to sense a concentration gradient of attractants and repellents of about 10,000 fold or 100,000 fold which is due to the negative cooperativity of W and A proteins - what is essential for that negative cooperativity are the che W and A proteins - W is a transducer that transmits the conformational information from R’ directly to che A che A is a sensor kinase -che A senses the conformation of R’ and W once it senses that it transmits the signal to the ATP dependent kinase activity of itself, that phosphorylates itself on a histidine residue which can then transfer the phosphate
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group to another protein called a Response Regulator so che A is a sensor, transducer, kinase, autokinase -Response regulator= che Y when phosphorylated goes to the basal region of the flagellum flagellar switch and controls the direction of rotation, causing the flagellum to rotate clock-wise direction the bacteria tumble and swim in all directions not really knowing where to go, and when the rotation reverts back to the normal rotation then they swim forward in a new location that’s how the bacteria knows they want to go in a different direction
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Microbial Physiology notes lec7 10-8-10 - Microbial...

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