Calculating the Minimum Amino Acids for Membrane Crossing | Protein MW 26,000 Da

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In summary, the question asks for the minimum number of amino acids needed for a single segment to span a 4.5 nm cell membrane, as well as the fraction of the protein involved in the membrane-spanning helices. The answer is 30 amino acids and 89% of the protein, respectively. The calculation involves taking into account the distance between amino acids in an alpha helix, as well as the number of amino acids required to make a turn at each end of the protein.
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flunkie
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[SOLVED] BioChem Amino acid

Homework Statement



A protein has a MW of 26,000 Daltons. The protein consist of 7 alpha helix segments that cross a cell membrane of 4.5 nm.

Homework Equations



What they want to know is the minimum number of AA's for a single segment to cross the membrane completely and the fraction of the protein involved in the membrane spanning helices.

The Attempt at a Solution



I really do not know where to being with this question and have been looking for a beginning for a while. I know the answers are 30 and 89%, but I don't know how to calculate them.

My thought process has led me to try (26000/(110x7)) the weight of the protein by the average AA weight and number of chains, but that brings me to 33.8. I also know that the 4.5 nm factors in there somewhere, but where? I have also tried (26000/(45x7x3.6) 45 is 4.5 nm in angstroms, 7 is the number of helices and 3.6 is the amount of AA's in one helix turn, but that makes it too low at ~23. As far as the fraction thing goes I figured I would figure out the first part and go from there.

Thanks for any help.
 
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You need to know something about the distance between amino acids in the alpha helix conformation described to figure out how many would span the membrane. Don't forget to count the number of amino acids required to make the turn at either end each time the protein passes through the cell membrane (I think that's what you forgot in your second attempt).
 
  • #3
Are you saying that I need to add on 2 turns of AA's to my final product?

If i did that for the second equation that would give me ~30 since there are 3.6 AA's per turn in a alpha helix, which is the right answer.

I figured out how to do the second part. That was just (30x110x7/26000) ~89%. AA's in helix, weight of AA, and 7 helices over the total weight of chain.
 

What is the chemical structure of amino acids?

Amino acids are organic compounds that consist of an amino group, a carboxyl group, and a side chain. They are also known as the building blocks of proteins.

What is the role of amino acids in the body?

Amino acids are essential for the human body as they are involved in various biological processes such as protein synthesis, hormone production, and tissue repair. They also play a key role in maintaining the health of muscles, bones, and the immune system.

How many amino acids are there in total?

There are 20 standard amino acids that are used to build proteins in the human body. However, there are also non-standard amino acids that have unique functions in the body.

Can amino acids be obtained from food?

Yes, most amino acids can be obtained from food sources such as meat, fish, dairy products, and plant-based proteins. However, some amino acids, known as essential amino acids, cannot be produced by the body and must be obtained through diet.

What is the difference between essential and non-essential amino acids?

Essential amino acids are those that the body cannot produce on its own and must be obtained through diet. Non-essential amino acids, on the other hand, can be produced by the body through various biological processes.

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