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Cystic fibrosis: amino acid deletion causes drastic results?

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Cystic fibrosis: amino acid deletion causes drastic results?

Postby junkeeroo » Thu Jan 14, 2010 11:13 pm

Cystic fibrosis is a genetic disease caused by a mutation in the gene that codes for a chloride channel membrane protein. In most patients, the mutation results in the loss of a single amino acid, which significantly affects the shape and function of the protein. How can the deletion of one amino acid lead to such drastic results?

Thanks again.
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Postby plasmodesmata11 » Fri Jan 15, 2010 1:02 am

are you familiar with tertiary structures of proteins? looking into those may help. I don't know specifics to Cystic fibrosis, but if a protein is missing an amino acid, it can become misshapen. because of this, it may not serve its purpose. The "key" won't fit the "lock", in other words.
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Postby mith » Fri Jan 15, 2010 6:56 am

one well studied example is in sickle cell hemoglobin

http://en.wikipedia.org/wiki/Sickle-cell_disease
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Re:

Postby JackBean » Fri Jan 15, 2010 7:13 am

mith wrote:one well studied example is in sickle cell hemoglobin

http://en.wikipedia.org/wiki/Sickle-cell_disease

Well, sickle-cell Hb has just one AA mutated, not missing, so it's a little different (but still there is change in the structure, but due to different reasons)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Re: Cystic fibrosis: amino acid deletion causes drastic results?

Postby jonmoulton » Fri Jan 15, 2010 4:26 pm

Cystic fibrosis can be caused by several different mutations. By Wikipedia, the most common mutation is the loss of a complete codon, with the net effect of the loss of a phenylalanine in the protein sequence.
http://en.wikipedia.org/wiki/Cystic_fibrosis#Cause

PubMed gives plenty to follow up on for that most common mutation:
http://www.ncbi.nlm.nih.gov/pubmed/?term=f508
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Postby junkeeroo » Fri Jan 15, 2010 7:57 pm

thanks, all. after some discussion and more reading, this is the answer i've come up with...

The sequencing of amino acids determines the shape of a protein, and the shape in turn determines the function(s) of a protein. With the deletion of one amino acid, there is an alteration in the shape and therefore functioning of the channel protein, i.e. the channel protein cannot work properly. As chloride is not transported into the cell as it should be, water cannot follow it, and so dehydration and stickiness of secretions occurs as is pathognomonic of cystic fibrosis.

have a great day!
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Postby jwalin » Sat Jan 16, 2010 6:17 am

you have covered everything but just in case you didn't understand the part regarding why it stops functioning with a change in shape.
chloride ion have a specific shape for it to pass through the channel should also have a specific shape.
now for example made of 3 parts
1. you have a pipe and a ball with a larger diameter the ball won't be able to pass.
2. and suppose you take the ball and a metal pipe with a larger diameter. the ball can pass. (this is the regular instance)
3. but now make a dent in the pipe somehwere in the middle. the ball gets stuck.

the loss of the specific a.a results in a change in shape.
now if you want to know how? please free to ask
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Postby JackBean » Sat Jan 16, 2010 9:22 am

jwalin: are you sure, it's working like this? In the case of discussed problem?
http://www.biolib.cz/en/main/

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