Proteins

[bellowbruins]

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Hello all,

I have a general question about proteins and how it works.

So, from what I have understood, increase temperature or harsh environment etc, the protein will unfold its conformational shape. But today, I realize as I was doing TPR exercise, they said " the addition of high temperatures leads to aggregation, not unfolding." So , I am all confused with the term, protein unfold , protein misfold, protein aggregation in regards to high temperature etc. I tried google it and they everything gives me random answers which makes me even more confused. I realized I have always regarded proteins wrongly thorughout my college life T. T Can anyone please give me brief summary of this of what concept am I missing in here? Thanks.

 

[theonlytycrane]

Proteins are composed of sequences of amino acids that often times require specific shape(s) to work well or do their job right. Changes in the environment, such as temperature increase, can cause the shape to change (misfolding) resulting in loss of protein function. Proteins usually do their job best within a specific temperature, pH range, etc so something like high temperatures can mess things up.

 

[aldol16]

They're wrong, unless they're talking about a specific protein. Generally, proteins will denature when they're heated up. There's something called a melting point of a protein and that's what it measures. Proteins that have unfolded are highly disfavored for the very same reasons why protein folding is favored. That is, the greasy residues are no longer buried and they don't like being in contact with water. So what happens is multiple unfolded protein molecules come together and they can aggregate. This way, their hydrophobics can all touch each other instead of the water.

 

[bellowbruins]

They're wrong, unless they're talking about a specific protein. Generally, proteins will denature when they're heated up. There's something called a melting point of a protein and that's what it measures. Proteins that have unfolded are highly disfavored for the very same reasons why protein folding is favored. That is, the greasy residues are no longer buried and they don't like being in contact with water. So what happens is multiple unfolded protein molecules come together and they can aggregate. This way, their hydrophobics can all touch each other instead of the water.

So just a quick question, when you say protein aggregation, that means proteins have misfolded?In this case, if theres high temperature or so, the protein will be misfolded not unfolded? So protein misfolding is not the same as protein unfolding?

 

[aldol16]

So just a quick question, when you say protein aggregation, that means proteins have misfolded?In this case, if theres high temperature or so, the protein will be misfolded not unfolded? So protein misfolding is not the same as protein unfolding?

That is another possible scenario. But let's keep this separate. Protein misfolding is not the same as protein unfolding. High temperatures generally cause protein unfolding. Check out protein melting point if you want a sense of how this is measured biochemically. Protein misfolding can also occur and misfolded proteins can have exposed hydrophobic residues (biochemists term any solvent-exposed hydrophobic residues as "sticky"). These sticky parts then cause aggregation when they find other sticky parts on another protein.

 

[workaholic181]

I had a biochem lab where "aggregation" in high heat referred to the primary structure of proteins being denatured by the high heat. This caused distinct proteins to lose function and kind of "crash" into each other ie aggregate. This significantly increases density of this mass. Anyway, that could be what they were referring to.