Chaperone Proteins - Video Tutorials & Practice Problems
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Chaperone Proteins
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Video transcript
So now that we've covered the basics of protein folding, in this video we're gonna talk about how proteins fold within a cellular environment using chaperone proteins. So some small proteins are able to quickly fold up into their native proper shapes without any outside intervention whatsoever. But typically, large proteins fold very slowly and because they fold slow, they're more likely to need help folding faster. And so why is it important that proteins fold fast? Well, it turns out that within a cellular environment, it's overcrowded with lots and lots of molecules. And so the slower that a protein folds, the more likely it's going to interact with a molecule that will disrupt and interfere with the proper protein folding process, and that will lead to misfolded proteins. And so misfolded and unfolded proteins can result in protein aggregates. And these protein aggregates are just clumps of proteins. But the protein aggregates are nonfunctional proteins, which means that they will not perform their normal job. And so many different diseases such as Alzheimer's and Parkinson's result from misfolded proteins called prions. And so it's in the cell's best interest to make sure that all of its proteins fold fast in order to prevent prions and prevent diseases. And so that's exactly where chaperone proteins come into play. And so chaperones are actually proteins themselves that physically bind to other unfolded proteins and use ATP or energy in order to increase the rate of correct folding. And by rate, we just mean the speed of the folding. And so they do that by physically binding to other unfolded proteins and preventing other molecules from interfering and disrupting the proper protein folding process. And so an example of chaperones are heat shock chaperones, which facilitate proper folding of proteins denatured due to pretty much any type of cellular stress, including heat. And so heat shock chaperones are actually misleadingly named because, they were essentially called heat shock chaperones because they were discovered while they were heat shocking cells. But heat shock chaperones are actually involved with helping proteins fold, that were denatured pretty much due to any type of cellular stress including changes in pH, decreases in temperature, increases in temperature, or even UV radiation. And so a specific class of chaperones are chaperonins. And so chaperonins are a class of chaperone that also use ATP or energy in order to assist in proper protein folding, But they specifically do that by creating a cage around the protein, the unfolded protein. And that creates a very nice environment where the unfolded protein can fold properly without any interference from other molecules. And so let's take a look at our example down below to compare molecular chaperones and chaperonins. And so on the left, what we have are chaperones, and on the right, we have chaperonins. So starting with the chaperones on the left, we know that when a protein is first produced, that it's produced as an unfolded protein. And so this orange squiggly line that we see here is an unfolded protein, and it could be that this unfolded protein results from denaturation as well due to lots of different types of stresses. So you could imagine that, it could be due to heat, for instance. And so, the So this is the ideal path here. But sometimes this path is slow and folding is slow, especially interfere with the prepper protein folding process and that will lead to interfere with the prepper protein folding process and that will lead to misfolding of the protein. And so over here, what we have is a mis folded protein. And we know from our lesson up above that misfolded proteins are at risk of protein aggregation, where they can form clumps of proteins that are non functional. And we know that prions are the names of, protein aggregates that cause diseases such as Alzheimer's and Parkinson's. And so it's in the cell's best interest to avoid this pathway right here, because this pathway will lead to disease. And so one of the ways that cells can avoid this pathway is by using chaperone proteins. And so, chaperone proteins will physically bind to the unfolded protein and prevent other molecules from interfering with the protein folding process. And they use ATP or energy in order to increase the rate of the proper protein folding to generate the native protein. And so through this process, over here, we're able to get to the native protein, shape faster without having to worry about misfolded proteins. However, what you'll also notice is that some chaperones are capable of interacting with misfolded proteins and refolding them back into their native shape. And so you can see that chaperones are able to, essentially influence multiple different areas within this diagram, and that's a helpful thing to, again, avoid this aggregation and avoid disease. And so, later in our course, we'll talk about another method that cells can use to avoid aggregation, and that is to mark misfolded proteins for degradation, so that they essentially chop down the protein into protein fragments that are not harmful. And so, this is not a process that chaperones are involved with. And again, we'll talk more about degradation later on in our course, so something to look forward to. And so over here on the right, what we have are chaperonins, and chaperonins are a specific class of chaperones that essentially isolate unfolded proteins into a cage. And so essentially what you see is that our unfolded protein is essentially embedded into a cage like area, where it's essentially secluded and no other molecules are able to enter to interfere and disrupt with the process. So, essentially it uses energy just like chaperones do. The only thing is that it creates this cage that uniquely identifies it as chaperonin. And so, moving forward in our next couple of practice videos, we'll be able to get practice with the concepts of chaperones and chaperonins, so I'll see you guys in those videos.
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Problem
Problem
Heat shock protein 70 (HSP70), a chaperone protein found in many organisms, is one of the most highly conserved proteins in all of biology. Which of the following statements about HSP70 is true?
A
HSP70 operates by forming a large cage around the unfolded polypeptide to increase its solubility.
B
HSP70 facilitates proper protein folding without the use of energy.
C
Cellular expression of HSP70 concentration significantly increases in high temperature environments.
D
Expression of HSP70 concentration decreases or stays constant in high temperature environments.
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Problem
Problem
Which statement most accurately characterizes the effect of high temperatures (>50˚C) on protein folding?
A
High temperatures increase the rate of protein folding so proteins adopt their native fold faster.
B
There is little to no effect of high temperature on protein folding.
C
At high temperatures, proteins are denatured but will re-fold into their native state upon cooling.
D
At high temperatures, proteins are denatured and at risk of forming intermolecular aggregates.
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Problem
Problem
Which of the following statements is false concerning Heat shock protein 60 (HSP60), a chaperonin protein.
A
HSP60 is required for some proteins to make their proper protein folding process spontaneous.
B
Like HSP70, HSP60 facilitates proper protein folding through binding & hydrolysis of ATP.
C
Cellular expression of HSP60 concentration increases in high temperature environments.
D
HSP60 operates by forming a large cage that the unfolded polypeptide enters to assume its native fold.