Phosphorylation

[dougkaye]

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Can someone explain to me what it actually means when a protein phosphorylates another? I know this takes place commonly in signal transduction but it seems too vague. Is ATP actually bound to a protein, and the protein phosphorylates the target protein thus becoming protein-ADP? How does this work exactly? AAMC #3 has a question (BS #116) where one protein phosphorylates another. R phosphorylates P, and according to the key, only protein R requires ATP for its action. It makes sense but I want to understand what's happening on a molecular level.

 

[flodhi1]

Can someone explain to me what it actually means when a protein phosphorylates another? I know this takes place commonly in signal transduction but it seems too vague. Is ATP actually bound to a protein, and the protein phosphorylates the target protein thus becoming protein-ADP? How does this work exactly? AAMC #3 has a question (BS #116) where one protein phosphorylates another. R phosphorylates P, and according to the key, only protein R requires ATP for its action. It makes sense but I want to understand what's happening on a molecular level.

In the phosphorylation process a protein gets phosphorylated as in a phosphate group gets attached to it. So this is what happens you have ATP Adenosine-5'-triphosphate (ATP) which has 3 phosphate groups). What the protein does is it removes that one phosphate group (PO4) and attaches it to the other protein. The new phosphorus group alters the role of the protein: it can activate, deactivate, or cause a change in function so in this case protein R takes 1 phosphate group from Adeno TRI phosphate and attached it to protein P. Thus protein P now has a phosphate group attached to it so it's (rich in energy- loose term and phosphorylated). So ATP lost the phosphate group and becomes ADP which is Adeno DI PHOSPHATE. Since it has 2 phosphate groups left ( Remember Protein R took one of ATPs phosphates and places it on P). Phosphorylation is extremely important because these Phosphate groups are rich in energy and like i stated before protein functions are altered e.g open channel ions, activate or inhibit other proteins etc.... but that goes into further detail. I hope that helped. 👍

 

[dougkaye]

In the phosphorylation process a protein gets phosphorylated as in a phosphate group gets attached to it. So this is what happens you have ATP Adenosine-5'-triphosphate (ATP) which has 3 phosphate groups). What the protein does is it removes that one phosphate group (PO4) and attaches it to the other protein. The new phosphorus group alters the role of the protein: it can activate, deactivate, or cause a change in function so in this case protein R takes 1 phosphate group from Adeno TRI phosphate and attached it to protein P. Thus protein P now has a phosphate group attached to it so it's (rich in energy- lose term and phosphorylated). So ATP lost the phosphate group and becomes ADP which is Adeno DI PHOSPHATE. Since it has 2 phosphate groups left ( Remember Protein R took one of ATPs phosphates and places it on P). Phosphorylation is extremely important because these Phosphate groups are rich in energy and proteins are unable to get activated. In many cases what happens is these phosphate groups activate proteins which can do several things e.g open channel ions, activate or inhibit other proteins etc.... but that goes into further detail. I hope that helped. 👍

That is a good explanation. Thanks! So in the reaction as described, is ATP just considered a reactant? It is dephosphorylated, and its high-energy phosphate is transferred to the receiving molecule, in this case protein P. I guess this makes sense, as it allows for the enzyme to remain unchanged (by definitional necessity).

 

[PiBond]

Phosphorylation generally changes the shape of the protein it adds onto. Phosphate groups are negatively charged and thus their addition to a polypeptide can cause a conformational change which can either activate or deactivate it.

 

[loveoforganic]

I guess this makes sense, as it allows for the enzyme to remain unchanged (by definitional necessity).

First, a protein isn't necessarily an enzyme. Even in the case of an enzyme being phosphorylated though, the enzyme is not "unchanged." Enzymes catalyze a specific reaction or type of reaction, and they only remain unchanged while catalyzing this specific reaction. Phosphorylation irreversibly (until dephosphorylated by another enzyme) changes an enzyme.

 

[flodhi1]

That is a good explanation. Thanks! So in the reaction as described, is ATP just considered a reactant? It is dephosphorylated, and its high-energy phosphate is transferred to the receiving molecule, in this case protein P. I guess this makes sense, as it allows for the enzyme to remain unchanged (by definitional necessity).

You can think of the ATP as a NECESSARY reactant if you're thinking of this in a Biochemical perspective. Without ATP present no phosphorylation or transfer of energy rich phosphate groups will occur! 👍 Just think of it as this you have 3 phosphate groups and I'm an enzyme. I come upto you I steal your phosphate away and give it to my friend that uses the phosphate. So now YOU got dephosphorylated you went from ATP (TRIphosphate) to ADP (DIphosphate) while my buddy got the third phosphate and is enjoying life! (Using it to open membrane channels, activate other proteins or get deactivated etc.... there's a huge list of things. ATP IS THE FOUNDATION of life, everything that goes on in your body is based off these energy rich phosphate groups)! You know how whenever we want to do something we use money right? we go to the grocery store we buy gum, bread, milk, gas whatever with money well the bodies currency is through these phosphate groups. If they want to do something they have to PAY just like you and me but their currency are these phosphate groups!

 

[Rabolisk]

You can think of the ATP as a NECESSARY reactant if you're thinking of this in a Biochemical perspective. Without ATP present no phosphorylation or transfer of energy rich phosphate groups will occur! 👍 Just think of it as this you have 3 phosphate groups and I'm an enzyme. I come upto you I steal your phosphate away and give it to my friend that uses the phosphate. So now YOU got dephosphorylated you went from ATP (TRIphosphate) to ADP (DIphosphate) while my buddy got the third phosphate and is enjoying life! (Using it to open membrane channels, activate other proteins or get deactivated etc.... there's a huge list of things. ATP IS THE FOUNDATION of life, everything that goes on in your body is based off these energy rich phosphate groups)! You know how whenever we want to do something we use money right? we go to the grocery store we buy gum, bread, milk, gas whatever with money well the bodies currency is through these phosphate groups. If they want to do something they have to PAY just like you and me but their currency are these phosphate groups!

What does the energetics of ATP have to do with phosphorylation of enzymes to change their conformation and their substrate binding affinity?

 

[shinbeats]

What does the energetics of ATP have to do with phosphorylation of enzymes to change their conformation and their substrate binding affinity?

It has a lot to do with it, it's based on the foundation of the first two laws of thermodynamics. Two high-energy phosphate bonds (phosphoanhydride bonds) (those that connect adjacent phosphates) in an ATP molecule are responsible for the high energy content of the ATP molecule. In biochemical reactions, these anhydride bonds are referred to as high-energy bonds.Energy stored in ATP may be released upon hydrolysis of the anhydride bonds. The bonds formed after hydrolysis—or the phosphorylation of a residue by ATP—are lower in energy than the phosphoanhydride bonds of ATP. During enzyme-catalyzed hydrolysis of ATP or phosphorylation by ATP, the available free energy can be harnessed by a living system to do mechanical work. With respect to your question reversible phosphorylation results in a conformational change in the structure in many enzymes and receptors, causing them to become activated or deactivated. I hope this clarifies the importance/role of these energy rich phosphate groups that flodhi1 is talking about.

 

[loveoforganic]

With respect to your question reversible phosphorylation results in a conformational change in the structure in many enzymes and receptors, causing them to become activated or deactivated. I hope this clarifies the importance/role of these energy rich phosphate groups that flodhi1 is talking about.

This doesn't relate to the energetics of ATP though, and that's all he was getting at.

 

[shinbeats]

This doesn't relate to the energetics of ATP though, and that's all he was getting at.

The OP posted, "AAMC #3 has a question (BS #116) where one protein phosphorylates another. R phosphorylates P, and according to the key, only protein R requires ATP for its action. It makes sense but I want to understand what's happening on a molecular level."

Can you explain to the OP how phosphorylation activates proteins and changes their conformation if the "energetics" of phosphate groups on ATP are unrelated to this? other than the energy rich phosphate bonds how does it do it? I would love to know because maybe I'm missing something important here.
Thank you

 

[Rabolisk]

The OP posted, "AAMC #3 has a question (BS #116) where one protein phosphorylates another. R phosphorylates P, and according to the key, only protein R requires ATP for its action. It makes sense but I want to understand what's happening on a molecular level."

Can you explain to the OP how phosphorylation activates proteins and changes their conformation if the "energetics" of phosphate groups on ATP are unrelated to this? other than the energy rich phosphate bonds how does it do it? I would love to know because maybe I'm missing something important here.
Thank you

In the narrowest sense, the energetics of ATP has nothing to do with the mechanism in which phosphorylation activates proteins. The introduction of a phosphate group on a serine, threonine, or a tyrosine residue introduces negative charges, which alters the structure and function of the protein. This is largely an electronic effect, and where the phosphate group came from is irrelevant. In a broad sense though, the reason why phosphorylation is so ubiquitous in life is of course fundamentally linked to the thermodynamics of ATP hydrolysis.

 

[loveoforganic]

Yeah, it sounds like you're getting too tied up in the role ATP serves as a coupling agent to provide energy for reactions. When a protein is phosphorylated, that phosphorylation could have been an endothermic reaction with Pi, the result would be the same

 

[shinbeats]

In the narrowest sense, the energetics of ATP has nothing to do with the mechanism in which phosphorylation activates proteins. The introduction of a phosphate group on a serine, threonine, or a tyrosine residue introduces negative charges, which alters the structure and function of the protein. This is largely an electronic effect, and where the phosphate group came from is irrelevant. In a broad sense though, the reason why phosphorylation is so ubiquitous in life is of course fundamentally linked to the thermodynamics of ATP hydrolysis.

This is basic common sense you could receive the phosphate from GTP too but I would suggest that you read the OPs question he specifically addressed ATP. Why compare apples with bananas. I'm pretty sure any pre-med has enough common sense to know that these phosphate groups do NOT only come from ATP. The point was that the BASIC fundamentals of these phosphate groups on ATP would also be similar to GTP or any other. The point was to convey to him the mechanical work that can be done by these phosphate groups that are "energy rich".

Yeah, it sounds like you're getting too tied up in the role ATP serves as a coupling agent to provide energy for reactions. When a protein is phosphorylated, that phosphorylation could have been an endothermic reaction with Pi, the result would be the same

Again I will state for the 100th time that the OP specifically addressed ATP in his question not once but twice. Plus I am aware of the AAMC #3 question he was addressing thus it would ONLY MAKE sense to explain to him the role of ATP and the phosphorylation of the protein. Why would I rant about inorganic phosphate, GTP etc... when he's asked about ATP.

 

[flodhi1]

lol calm down fellas