Doesn't allactose have a repressor actitivy over the LacI. So, why it is called as inducer? Probably you mean the allactose as a inducer for operator??
True, I suppose the term "inducible" is confusing in this context. It is "induced" by allolactose to undergo a conformational change ("induced" by a presence of inhibitor) and thereby "inducing" the operon ("inducing" is a lack of repressor at the operator). Some articles also refer the "I" in lacI to be "inhibitor", which I guess is a better description than "inducible". I appreciate you catching the discrepancy. I will pin your comment, so others can notice it 🙂
Great video! The level of Glucose wont be high enough as it will be metabolized in Glycolysis (?) and I guess there will also be an enzyme which controls the adenylylcyclase, which, at a distinct concentration of Glucose in the cell, will inhibit the adenylylcyclase. When this happens, the cell will/musst switch to Glucose as the CRP is inactivated again. Thanks for the content.
True! Glucose won't be high enough because it gets used in energy production (Glycolysis for instance). But I don't quite agree with the second half of your explanation - glucose itself controls adenylyl cyclase (see 22:55 in the video) . In my opinion, the glucose is not high enough to inhibit the Adenylyl cyclase, so the CRP/CAP remains active. Therefore, no negative feedback at limiting glucose concentrations. The cell will switch out of lac operon if Glucose concentration exceeds the threshold concentration for repressor inactivation as well as adenylyl cyclase inactivation.
@@theCrux Yes, I guess your right. I was confused with the PTS-System, as the EIIA^Glc [Phosphorylated] Protein needs to bind to the Adenylyl cyclase to be active. I was to unsure about the mechanism and thought it would be phosphorylated by some enzyme, but it just stays phosphorylated if there is no Glucose. Thanks!
@@sharisto354True...We maximum time think that extrinsic regulation like modifications can be the case....But we never thought of dynamics as like @theCrux explained....Btw awesome content
nice video....very detailed explanation....that has made my concept clear the answer of the last question may be as soon as glucose is produced by breakdown of lactose it should be utilized by the cell for energy formation through glycolysis and then other respiratory processes
I am glad the video was useful :) And you are correct with the answer that the glucose (which is produced at a low concentration) gets used up in energy production, so it cannot form a negative feedback at such low levels 🙂
very nice presentation. I have a question, how many untranslated regions does the mRNA of the lacZYA has? Is it one 5 prime untranslated in the beginning and one 3 prime in the finish, or one 5 prime and one 3 untranslated region for each structural gene?
There is a UTR between each structural gene. They are 5' or 3' depending on which structural gene you are talking about. UTR is ~50 bp between Z and Y and ~80 bp between Y and A.
When the repressor binds to the main operator and the downstream operator, is it any more or less effective than when it binds to the main and upstream operators?
Great question! The upstream + main operator combination is overall more effective than downstream + main operator since there are more chances for the upstream to loop. Most all processes are dynamic states and more often you can transition into a state the better the outcome. So by that logic the main + upstream has a better outcome to negative regulation. The binding strength as an absolute measure between upstream and downstream is not that different.
True, it is too low but that is not an observation but a mechanistic explanation to why it doesn't repress the operon :) You are on the right track to the answer. Hint: Think about where glucose may be used by the cell.
Nice explanation , Nice & colourflul n correct....informative.....deep execution....no words further.....for my expression. Thank you very very much for this. Now answer ....it may be because of initial high concentration of lactose and little concentration of glucose....I think so....
I am glad you found the video useful. For the answer: You are correct in saying that the concentration of glucose is low relative to lactose. But that is just the starting point of the answer :) At a deeper level, it would be better to say that the concentration of glucose is not high enough to actually have any impact on the cAMP pathway because the little glucose that is produced by lacZ ends up in glycolysis 🙂
