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Old 04-16-2011
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Biochemistry Amino acid structure question

A stretch of 25 hydrophobic amino acids in a protein could be located in

1 signal sequence
2 triple helix
3 stop transfer sequence
4 start transfer sequence
5 transmembrane domain
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Old 04-16-2011
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Wow - I eliminated all of the answer choices...

1, 3, 4: signal sequences and start/stop transfer sequences are usually hydrophobic and usually not that long.
2: collagen? I wouldn't have thought of glycine or proline as being "hydrophilic" exactly...
5: I eliminated this one first...

No idea - if I had to guess I would choose Signal Sequence?
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Old 04-16-2011
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Sorry, Mondoshawan, I had a typo, it should be "hydrophobic".

You are right, answer is #2, triple helix collagen
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Old 04-17-2011
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Seriously! do they ask such questions in Step 1
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Old 04-18-2011
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I think Hydrophobic amino acids can be a part of transmembrane protein. so why can't it be E.
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Old 04-18-2011
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Hi, Dr. Ram:

The key is stretch (all hydrophobic amino acids are side by side) of hydrophobic amino acids present in the structure. Only triple helix has this feature.
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Old 04-18-2011
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Quote:
Originally Posted by usluipek View Post
Hi, Dr. Ram:

The key is stretch (all hydrophobic amino acids are side by side) of hydrophobic amino acids present in the structure. Only triple helix has this feature.
and so many - it would only take a dozen or less hydrophobic aa's to span a membrane, I think..
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