MIC 360 Lecture Notes - Lecture 25: Demethylation, Prs For Music, Methyltransferase
Monday, April 23, 2018
MIC 360 Class 25
1. Control of the bacterial motility!
-Flagella = mechanic machine that offers the movement of the bacteria in either
swimming or swarming!
-Clockwise = make bacteria tumble; counterclockwise makes bacteria go straight!
-Bacteria move towards nutrient rich environment and escape from nutrient depleted
environment!
-Can be determined by bacteria growth on solid agar surface!
-Movement of bacteria = swarming!
-Start from original culture area and spread out toward the area where there was no
bacteria grown!
-Area has higher concentration of nutrients!
-When bacteria consumes nutrient in location where it first grew = depletes its
nutrient concentration, thus bacteria start to move out!
-Concentration of attractant are sensed by at least 4 MCPS!
-sMethyl accepting chemotaxis protein!
-Can be methylated or demethylated by CheR or CheB!
-CheB can demethylate the methylated MCP !
-Contrarily, CheR can methylate the MCP on the right (of slide)!
-Remember Dam Protein: it’s a DNA methylator!
-CheR is a protein methylase
-The state of activity is started from MCP methylation or demethylation!
-CheY = two component regulator!
-Regular two component regulator plays a role in DNA binding to a specific
promoter!
-Stimulates and represes gene expression!
#1
find more resources at oneclass.com
find more resources at oneclass.com
Monday, April 23, 2018
-Phosphorylated CheY can directly bind to flagella motor rotor and therefore
turn the rotor clockwise!
-When CheY (phosphorylated) binds to the rotor, then bacteria start to tumble
rather than go straight !
-The attractant binds to the MCP (not the sensor)!
-MCP transduces signal to the kinase ( formed by CheA and CheW proteins)
-It is CheA that has kinase activity!
-This kinase activity once stimulated can do two different phosphorylations !
-When the kinase can be activated = when the MCP on the right is
methylated. When this MCP can form a methylated state is when the
attractant’s concentration is reduced!
-When the concentration is high then the kinase on the left is inhibited!
-The activated kinase on the left indicates decrease in attractant!
-When activated it phosphorylated CheY to turn the rotation to clockwise!
-When attractant concentration towards the direction is increasing, and
kinase activity is off, then the kinase on the right is not able to
phosphorylate CheY and therefore does not bind to the rotor, then rotor
actually takes counterclockwise rotation!
-Only when bacteria moves will the concentration change!
-When bacteria stay in one particular point = the gradient disappears!
-Then bacteria have to move around and sense the gradient and move again!
-Has to be a dynamic process for the signal transduction to keep the bacteria to
move towards or start tumbling!
-It’s sensing the gradient but not the concentration again!
-The stimulation has to keep escalating or things will not change!
-There is another protein called CheZ!
-Can keep dephosphorylating phosphorylated CheY!
-ONce you have CheY - one opportunity = bind to the rotor to turn clockwise!
#2
find more resources at oneclass.com
find more resources at oneclass.com
Monday, April 23, 2018
-Or dephosphorylate and turn counterclockwise!
-Second function of kinase is to phosphorylate CheB!
-Phosphorylated CheB can de- phosphorylate MCP!
-This kinase can phosphorylate two proteins!
-The kinase is not a regular kinase from one two component system!
-It instead has ability to phosphorylate both CheB and CheY!
-The kinases are the same MCP, just depends on which one gets phosphorylated
and then the other gets de-phosphorylated!
-
2. Chemotaxis Pathways of E. coli!
-Summary of MCPs for the exam!
-Read the slide!
3. Signal Transduction in Chemotaxis!
-Another summary slide to use for exam!
-Difference with two component system:!
-Multiple sensors transduce the signal to the kinase and then pass to the
phosphoregulator!
-Does not directly regulate gene expression!
-Can phosphorylate multiple proteins!
4. Plasmid!
-Plasmid is a unique entity in most prokaryotic organisms!
-In eukaryotes there are no plasmids!
-There’s no system to replicated!
-Plasmid is a extrachromosomal DNA capable of conferring a selective advantage
upon the bacteri Ain which they occur!
#3
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Mic 360 class 25: control of the bacterial motility. Flagella = mechanic machine that o ers the movement of the bacteria in either swimming or swarming. Clockwise = make bacteria tumble; counterclockwise makes bacteria go straight. Bacteria move towards nutrient rich environment and escape from nutrient depleted environment. Can be determined by bacteria growth on solid agar surface. Start from original culture area and spread out toward the area where there was no bacteria grown. When bacteria consumes nutrient in location where it rst grew = depletes its nutrient concentration, thus bacteria start to move out. Concentration of attractant are sensed by at least 4 mcps. Can be methylated or demethylated by cher or cheb. Contrarily, cher can methylate the mcp on the right (of slide) Remember dam protein: it"s a dna methylator. The state of activity is started from mcp methylation or demethylation. Regular two component regulator plays a role in dna binding to a speci c promoter.
