In ballpark figures, can anyone tell me what the average number of cysteine residues per (bovine) serum protein is? For instance, albumin has 35 cysteine residues out of some 580 total residues, so about 6% of BSA is cysteine residues. Is that a little, a lot or an average value compared to other serum proteins?
Hi Teodora, I'm a bit confused about your question.
Every protein in blood has the cysteine residues that are required for their normal structure and function. This is determined by natural selection and not by the law of averages.
Hi Teodora,
the albumin is the most important serum protein (that covers about the 55% of total serum proteins).
So, considering that the primary conserved structure of albumins is
xxCxxxxxxxxxxxxxxxxCCxxCxxxxCxxxxxCCxxxCxxxxxxxxxCxxxxxxxxxxxxxxCCxxxxCxxxx
(where C is cysteine and x is a general amino acid. the sequence taken from wikipedia http://en.wikipedia.org/wiki/Albumin)
you can estimate that the average number of cysteines in blood proteins is about 12.
Bye!!
Thank you.
First of all, I was not suggesting in any way that the number of cysteine residues is determined by the law of averages. However, albumin has about 6% cysteine residues. I was wondering if, compared to other serum proteins, that is a lot, a little, or similar number. So, for instance, are there proteins that have say 20% cysteine residues, or 0.5% and if so, do a lot of the serum proteins have values much lower or much higher than the value for BSA?This does not take into account the abundance of each protein in serum
Secondly, imagine a theoretical scenario where you take a serum sample and brake it down into amino acid residues, count the total number of residues, the total number of cysteine residues and then say cysteine is x% of all amino acid residues. What would x be in this case?
Check amino acid codon usage. 23.2 out of every 1000 codons in a mouse code for cysteine. The median protein is 384 amino acids. 384 * 23.2/1000 = 8.9 cysteines in the median protein. Therefore, albumin seems to be an exception unless my math or logic is incorrect. Since albumin is 50% of serum protein, it will increase the number of cysteines for the average serum protein significantly.
https://www.genscript.com/tools/codon-frequency-table
- Badges
- Science topic
- Similar topics
- Biological Science
- Molecular Biology
- Biomolecules
- Proteins