Biology question

[Mo0o]

In transcription, the sequence called the operator, is that for repressor proteins only or for activators as well? Im having trouble figuring this point out. One textbook says its for both while another book says its only for repressors. My impression was that any regulatory protein will bind to operator sequences, but looking at the lac-operon example thers only one operator and its only applied to the lac-repressor protein.

 

[eigen]

it is for repressor proteins.

 

[Isshinryu]

lac-repressor only. What text book says both?

 

[Mo0o]

Griffith, 2nd edition:

...DNA segments near the promoter serve as protein binding sites--most of these sites are termed operators--for regulatory proteins called activators and repressors.

 

[Isshinryu]

Originally posted by: Mo0o
Griffith, 2nd edition:

...DNA segments near the promoter serve as protein binding sites--most of these sites are termed operators--for regulatory proteins called activators and repressors.

lac-repressors bind to the operator, downstream from the promoter
CAPs bind to the cyclic AMP and a sequence of 16 base pairs upstream from the promoter

 

[Mo0o]

Originally posted by: Isshinryu

Originally posted by: Mo0o
Griffith, 2nd edition:

...DNA segments near the promoter serve as protein binding sites--most of these sites are termed operators--for regulatory proteins called activators and repressors.

lac-repressors bind to the operator
CAPs bind to the cyclic AMP and a sequence of 16 base pairs upstream from the promoter

My question is why dont they call the place where the CAPs bind to the operator as well. What sets an operator apart from other promoter sequences.

 

[Isshinryu]

Originally posted by: Mo0o

My question is why dont they call the place where the CAPs bind to the operator as well. What sets an operator apart from other promoter sequences.

That's what they're named. Repressors bind the the Operator (Silencer), the CAPs bind to the CAP site. I don't know how else to answer that question...

 

[Mo0o]

Originally posted by: Isshinryu

Originally posted by: Mo0o

My question is why dont they call the place where the CAPs bind to the operator as well. What sets an operator apart from other promoter sequences.

That's what they're named. Repressors bind the the Operator (Silencer), the CAPs bind to the CAP site. I don't know how else to answer that question...

I mean in general operons. Not just the lac operon specificially.

 

[screw3d]

Damn... I learning the same thing too.. midterm on Friday

 

[bleeb]

Damn I'll be learning this stuff pretty soon! I'm getting worried!

 

[Isshinryu]

Originally posted by: Mo0o

Originally posted by: Isshinryu

Originally posted by: Mo0o

My question is why dont they call the place where the CAPs bind to the operator as well. What sets an operator apart from other promoter sequences.

That's what they're named. Repressors bind the the Operator (Silencer), the CAPs bind to the CAP site. I don't know how else to answer that question...

I mean in general operons. Not just the lac operon specificially.

In general, the Operator is nothing more than the binding site for a repressor protien so that transcription is prevented. There's nothing more to that.

 

[spidey07]

Bad repressor protien! We must free the operator and end the repression!

 

[Mo0o]

Originally posted by: bleeb
Damn I'll be learning this stuff pretty soon! I'm getting worried!

it's really not that bad, my book has bad wording thats all.

 

[Isshinryu]

Originally posted by: Mo0o

Originally posted by: bleeb
Damn I'll be learning this stuff pretty soon! I'm getting worried!

it's really not that bad, my book has bad wording thats all.

What class is this? Sophmore Mol. Bio?

 

[Mo0o]

Originally posted by: Isshinryu

Originally posted by: Mo0o

Originally posted by: bleeb
Damn I'll be learning this stuff pretty soon! I'm getting worried!

it's really not that bad, my book has bad wording thats all.

What class is this? Sophmore Mol. Bio?

Yeah, they call it Genetics and Cell Biology, really not that bad of a class altough the professor is boring as hell

 

[Isshinryu]

Originally posted by: Mo0o

Originally posted by: Isshinryu

Originally posted by: Mo0o

Originally posted by: bleeb
Damn I'll be learning this stuff pretty soon! I'm getting worried!

it's really not that bad, my book has bad wording thats all.

What class is this? Sophmore Mol. Bio?

Yeah, they call it Genetics and Cell Biology, really not that bad of a class altough the professor is boring as hell

Cool, I took that class this time last year. It was pretty fun, but we had a really crazy professor.

 

[Siva]

Wow, I have yet to learn anything in my sophmore cell/molecular bio.... I barely understand half the stuff discussed here. Bad professors suck

 

[stankonia3000]

Originally posted by: Mo0o
Griffith, 2nd edition:

...DNA segments near the promoter serve as protein binding sites--most of these sites are termed operators--for regulatory proteins called activators and repressors.

Because operons can be under negative or positive control (or both). In negative control, the repressor binds to the operon, turning it off. In positive control, the activator binds to the operator, activating the operon. The lac operon is under both negative and positve control. CRP is involved in the positive control and the repressor molecule in the negative control.

 

[OutHouse]

hold on let me get Saladin, its a door stop now.

 

[screw3d]

Which book are you using?

I just studied through my text (Biology 6th Edition, Campbell & Reece) and I pretty much got it already.

 

[Isshinryu]

Originally posted by: stankonia3000

Originally posted by: Mo0o
Griffith, 2nd edition:

...DNA segments near the promoter serve as protein binding sites--most of these sites are termed operators--for regulatory proteins called activators and repressors.

Because operons can be under negative or positive control (or both). In negative control, the repressor binds to the operon, turning it off. In positive control, the activator binds to the operator, activating the operon. The lac operon is under both negative and positve control. CRP is involved in the positive control and the repressor molecule in the negative control.

The activator never binds to the operator, that defies the very definition. It binds to the CAP, which is upsteam of the promoter, while the operator is always downstream of the promoter.