Predict domain strucutre by amu and percentage of secondary structure

[./Jack]

Hello everybody,

I'm doing my biochemistry exam review and stumbled upon a question from last years exam, I really can't get anything out of google.
The question goes as follows:

Quote

 

The two 10 kDa domains of γ-crystallin contain mostly (>90%) β-sheet secondary structure. Each domain will most likely be comprised of:

A. A single β-sheet of parallel β-strands connected by β-turns (reverse turns).
B. Two β-sheets made of parallel β-strands connected by short helices.
C. Two β-sheets made up of antiparallel β-strands.
D. A single β-sheet of antiparallel β-strands, so the two domains can pack against each other.

 

Correct is answer C. However, I can't quite figure out why. My reasoning so far:

-> If the Beta strands were connected by (short) alpha helices, the protein wouldn't be 90% Beta sheets, so B is out.

-> I've never heard of domains packing against each other, and since they fold independently, I don't think this is right.

But this is both rather washy reasoning. I can't figure out what information the "two 10 kDa domains" is supposed to give me.

 

Thank you for your time and any tips 

Jack

[Vmedvil]

3 hours ago, ./Jack said:

Hello everybody,

I'm doing my biochemistry exam review and stumbled upon a question from last years exam, I really can't get anything out of google.
The question goes as follows:

Correct is answer C. However, I can't quite figure out why. My reasoning so far:

-> If the Beta strands were connected by (short) alpha helices, the protein wouldn't be 90% Beta sheets, so B is out.

-> I've never heard of domains packing against each other, and since they fold independently, I don't think this is right.

But this is both rather washy reasoning. I can't figure out what information the "two 10 kDa domains" is supposed to give me.

 

Thank you for your time and any tips 

Jack

Here is what two anti parallel DNA would look like does it look like that?

[BabcockHall]

A is not a reasonable answer, either.  Antiparallel strands can be connected by beta-turns, but I don't see how parallel strands could be.  As a generalization, I don't see why domains cannot pack against each other.  However, I think that answer D is internally inconsistent.  See what you can do with that.

Edited November 14, 2017 by BabcockHall