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12. Gene Regulation in Prokaryotes

Arabinose Operon


Arabinose Operon

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Hi in this video we're gonna be talking about the opera. So the ravenous opera is responsible for encoding genes that control the breakdown of revenues and what is that? It is a sugar. So when there's a lot of arab knows present, the sal wants to break it down and therefore it does that through activating the opera on. Um and if Robin knows is not present, it doesn't want to waste the energy producing those jeans and those proteins. And so when A Robin knows is not there, it wants to repress the transcription of the opera. So how does it do that? Well, there are two regulatory regions you need to know about the A. R. A. I. Which is also called the initiator and the A. R. I. O. Regions. And these are DNA sequences actually just upstream of the Robin knows Opera on. And so how are they activated or repressed? Well there's a certain protein called R. A. C. So when Robin knows is present. So when there's an abundance of this sugar, the A. R A C binds the A. R. A one side or the initiator site and that initiates transcription. Which makes sense. Right? But there's also a second thing that is also required for initiating transcription and that is the C. A. M. P cap complex. Now you may remember this complex um via the glucose regulation of the lac opteron. So if you're unfamiliar with how this complex works or you've never heard of it before, I would go back and review this video because this glucose like opera on video really goes into detail how the camp cap complex works to activate operations. So in this case there's also a binding site for this complex and that also helps to initiate transcription. So that's initiation. The A. R. C binds the R. E. One and the C. A. M. P. Cap complex are both binding and they activate transcription. But when A Robin knows is not present, how is that inactivated? How is that transcription repressed? Well how it is is it's done through the same protein A. R. A. C. But instead of just finding the A. R. A. I. Or the initiator site, it binds both the A. R. A. I. And the A. R. A. O. And that represses transcription. And how it does this, how it represses is because it forms a DNA loop that prevents the plain rice from binding. So let me show you what that looks like. So here we have the opteron. So there would be jeans here, right? So I'm just drawing jeans. There are Robin knows um genes part of this operation that would break down ravenous. So when we have the R. A. C. Protein and when arab in moses present, what happens is it only binds the R. A. A site in addition to that there's this camp cap complex that comes in and binds to an adjacent site as well and this helps to activate the opera on that will break down the sugar. Now if Robin knows is not present. So if I just scribble it out here say okay well it's not present. Then what happens is the A. R. A. C. Protein also binds the A. R. A. O. Site which is here and when it does it actually folds this D. N. A. Up to the side of the protein and it will create a DNA loop. And when the D. N. A. Is looped like this then that is prevents preliminaries is from binding and therefore transcription cannot occur if the preliminaries can't bind so the R. A. C. Protein depending on which side is bind to, whether it's bound to just one the initiator or both. That determines whether or not there are avenues operation is activated or inhibited. So with that let's not move on.

The genes in the arabinose operon are responsible for what?


When arabinose is present, the arabinose operon is what?