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Natasha_4902
#1 Posted : Thursday, August 06, 2020 5:15:54 AM
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Hi,

For passage 4 of the bio and biochem section of AAMC full length 2, why does denaturing a protein make it weigh less? Isn't it the same amount of material just unfolded?

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INSTR_Katerina_102
#2 Posted : Thursday, August 06, 2020 7:45:50 PM
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Hi Natasha,

I don't have access to the AAMC exams so if you could give more information this would help.

However, what I can generally say is that significantly changing the conformation of or denaturing a protein/piece of DNA that is running on a gel will change how it runs on a gel without changing its mass.

I hope this helps!

Katt
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Natasha_4902
#3 Posted : Friday, August 07, 2020 6:13:24 AM
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Hi Katt,

The protein travelled from the distance of a 200kda protein when it was in its native form to the distance of a 100kda protein when it was denatured.

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INSTR_Katerina_102
#4 Posted : Saturday, August 08, 2020 2:32:54 AM
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Hi Natasha,

Ok, that doesn't seem to line up with the slight differences one would expect from a change in conformation.

My guess based on the information given is that this protein exists as a 200 kDa homodimer, and when you denature it each of the monomers runs at 100 kDa.

Again, I'm not sure without access to the question, but I hope this helps!

Katt
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INSTR_Katerina_102
#5 Posted : Wednesday, August 12, 2020 9:09:23 PM
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Hi Natasha,

Thanks for your email.

You are correct, normally when you denature a protein you should expect to see around the same mass because it is the same protein but unfolded.

However, when you first isolate a protein you might not be able to say for sure its quaternary structure - that is, it could be two different polypeptide chains linked together with intermolecular forces.

In this case, we can deduce because in:

1.Native we see one band at 200 kDa
2. Denatured conditions we see one band at 100 kDa

To me, the most likely explanation is that there are two homodimers linked together, and we couldn't see this under native because they moved as one unit.

This makes sense because the total mass is the same 100 + 100 = 200 kDa, and when you seperate the two chains from each other you would expect to see them run further due to their smaller mass.

Please let me know if this is still unclear,

Thanks,

Katt
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