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Postby 2810712 » Tue Mar 15, 2005 12:14 pm

From this conversation, prions are proteins, they change the conformation of
theis isomers[ differing in conformation] , right. But, then , I think, those changedPrPcs become PrPSc's , isn't it???
:?: Does those prions have any physiological IMP???
OK they can induce the pritein kinase K resistance etc. which prevents the degradation of that protein as its binding site changes due to conformational change.
:?: But, we can't say that this leads them to continue their all functions, as the conformational change will also affect the functioning of that protein.
:idea: But, this may be useful to block a cascade of reactions,; if we add some prions for a specefic protein in the cell then the digestion of that protein will not occur, or get reduced. { I think, prions are potent conformation changers] So, the path of biochem. reaction, which requires the digested parts of that protein , will not occur, isn't it???

Oh I've been a bit complicated here, sorry. :cry:

hrushikesh
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Postby abhay » Sat Mar 19, 2005 9:33 pm

Well too many questions??? a bit stuffy but let us sort it out one by one...

Does those prions have any physiological IMP???
Yes of course it has got some role as is evident from its constitutive nature of expression. over and above it is found abundantly inside Central nervous system.. but then its exact nature of its function is not properly understood.
workers have found its role in copper homeostasis, response to oxidative stress. exact function is still an enigma for science.

OK they can induce the pritein kinase K resistance etc. which prevents the degradation of that protein as its binding site changes due to conformational change.
let me correct u for proteinase K. its an serine endoproteases which acts non specifically on proteins. result is massive proteolysis. this enzyme is used as an assay for detection of scrapie protein as this protein is not degraded by proteinase K enzyme. reason behind this in ability may be attributed to inaccessibility of peptide bond to this enzyme..(as u have mentioned in u'r post).


But, we can't say that this leads them to continue their all functions, as the conformational change will also affect the functioning of that protein

surely, it is not able to function properly. after its conformation changes it is shed off from cell membrane and thus it deposits extracellularly causing formation of amyloid plaques. this shedding is done by a phospholipase which specifically cuts GPI anchor of this protein.



But, this may be useful to block a cascade of reactions,; if we add some prions for a specefic protein in the cell then the digestion of that protein will not occur, or get reduced. { I think, prions are potent conformation changers] So, the path of biochem. reaction, which requires the digested parts of that protein , will not occur, isn't it???

well there i disagree with u'r point.. pricipally if it can change conformation of any other proteins it should act in the way u have mentioned.. but unfortunately sytem is not as simple as assumed..
in case of prion protein "species barrier" is reported. that means prion of human wont transform mouse prion.. this give a sense of a very high specificity. moreover no body has reported any cross conformation changes among different proteins. reason lies behind the structure of beta sheet formed by different proteins. if we assume this structure as a platform or any protein domain.. then only those proteins having same domain/platform can sit and can enjoy the priviledge of conformational changes.. and in this case it is possible for same protein.. thus we should always look the system keeping in view of high specificity of this protein.. thus u'r biochemical reaction wont stop even if u add this protein. nevertheless it will affect reaction by crowding or quenching metal ions or bybinding to substrate or enzymes( incase if it has got property to bind to it.)

I'll suggest to everybody if they are really interested in Prion biology please visit Nobel prize site and read lecture of Prusiner (1997).
or follow this link:
http://nobelprize.org/medicine/laureates/1997/prusiner-lecture.html
wishes,
abhay
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Postby abhay » Sat Mar 19, 2005 9:35 pm

Well too many questions??? a bit stuffy but let us sort it out one by one...

Does those prions have any physiological IMP???
Yes of course it has got some role as is evident from its constitutive nature of expression. over and above it is found abundantly inside Central nervous system.. but then its exact nature of its function is not properly understood.
workers have found its role in copper homeostasis, response to oxidative stress. exact function is still an enigma for science.

OK they can induce the pritein kinase K resistance etc. which prevents the degradation of that protein as its binding site changes due to conformational change.
let me correct u for proteinase K. its an serine endoproteases which acts non specifically on proteins. result is massive proteolysis. this enzyme is used as an assay for detection of scrapie protein as this protein is not degraded by proteinase K enzyme. reason behind this in ability may be attributed to inaccessibility of peptide bond to this enzyme..(as u have mentioned in u'r post).


But, we can't say that this leads them to continue their all functions, as the conformational change will also affect the functioning of that protein

surely, it is not able to function properly. after its conformation changes it is shed off from cell membrane and thus it deposits extracellularly causing formation of amyloid plaques. this shedding is done by a phospholipase which specifically cuts GPI anchor of this protein.



But, this may be useful to block a cascade of reactions,; if we add some prions for a specefic protein in the cell then the digestion of that protein will not occur, or get reduced. { I think, prions are potent conformation changers] So, the path of biochem. reaction, which requires the digested parts of that protein , will not occur, isn't it???

well there i disagree with u'r point.. pricipally if it can change conformation of any other proteins it should act in the way u have mentioned.. but unfortunately sytem is not as simple as assumed..
in case of prion protein "species barrier" is reported. that means prion of human wont transform mouse prion.. this give a sense of a very high specificity. moreover no body has reported any cross conformation changes among different proteins. reason lies behind the structure of beta sheet formed by different proteins. if we assume this structure as a platform or any protein domain.. then only those proteins having same domain/platform can sit and can enjoy the priviledge of conformational changes.. and in this case it is possible for same protein.. thus we should always look the system keeping in view of high specificity of this protein.. thus u'r biochemical reaction wont stop even if u add this protein. nevertheless it will affect reaction by crowding or quenching metal ions or bybinding to substrate or enzymes( incase if it has got property to bind to it.)

I'll suggest to everybody if they are really interested in Prion biology please visit Nobel prize site and read lecture of Prusiner (1997).
or follow this link:
http://nobelprize.org/medicine/laureates/1997/prusiner-lecture.html
wishes,
abhay
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Postby abhay » Sat Mar 19, 2005 9:54 pm

oops i'm sorry for sending two posts having same but minor differences in the content.
wishes,
abhay
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Postby 2810712 » Mon Mar 21, 2005 7:53 am

ABHAY WROTE-
well there i disagree with u'r point.. pricipally if it can change conformation of any other proteins it should act in the way u have mentioned.. but unfortunately sytem is not as simple as assumed..
in case of prion protein "species barrier" is reported. that means prion of human wont transform mouse prion.. this give a sense of a very high specificity. moreover no body has reported any cross conformation changes among different proteins. reason lies behind the structure of beta sheet formed by different proteins. if we assume this structure as a platform or any protein domain.. then only those proteins having same domain/platform can sit and can enjoy the priviledge of conformational changes.. and in this case it is possible for same protein.. thus we should always look the system keeping in view of high specificity of this protein.. thus u'r biochemical reaction wont stop even if u add this protein. nevertheless it will affect reaction by crowding or quenching metal ions or bybinding to substrate or enzymes( incase if it has got property to bind to it.)

WHat if we introduce a prion specefic for a target protein to stop the functioning of that orotein ? ? ? Can we obtain prions specefic for some protein ? ? ?
Also if it is possible then other problems like binding to substrate or enzyme will, i think, not ocur, as their affinity for binding prions would be lesser than that specefic protein, what do U think???

hrushikesh


_at_ Abhay
that prion paper was good ,but I didn't read it completely . sorry but it was too long .


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Postby abhay » Mon Mar 21, 2005 9:08 am

WHat if we introduce a prion specefic for a target protein to stop the functioning of that orotein ? ? ?
well its not possible to rule out the possibility of making prion specific to any protein.. but i feel the word usage is a bit wrong .. rather than saying prion specific to any protein u can tag any protein with prion sequence (responsible for aggregation) and then see whatever happens to it. its just like tagging any protein with GFP to observe that protein in live cells using fluorescence microscopy...
so if u tag any protein with this prion.. outcome will be crowding of u'r protein as this sequence will aggregate and in that case u'r local protein concentartion will increase...
again hypothetically if this happens.. u'r protein activity will increase even in nanomolar concentration .. thus saving much of u'r protein.. but other side of the story is u'r protein may not feel happy in crowded condition or u'r substrate may not be accessible to all proteins due to overcrowd and thus u'll have reduced activity or u'r protein may precipitate out.. so u can see if u mangae to go for the optimum concentration of course u'll get something but again that will vary protein to protein...

over and above this protein is highly dangerous as it owes infectivity.. it needs P4/BSL4 facility.. so playing around with this protein may invoke ethical issue landing u in court..
but again these are just another aspects.. and nothing is impossible..
wishes,
abhay
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thnks

Postby 2810712 » Mon Mar 21, 2005 11:43 am

Thanks , questioning helps me understand better. Although I am not required to study this, questioning and trying to understand such topics helps even college students like me.
THank you Abhay, good to see [ see the name] somebody from my country here.
Thanks.

hrushikesh
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Postby abhay » Mon Mar 21, 2005 12:15 pm

no need to mention that. i'm impressed with your curious nature.. well i know this forum is not meant to ask any personnal questions but i'll be glad to know u'r whereabouts esp. u'r combi in college.. to avoid this forum with personnal details u can send me mail in following address..
[url]abhay@ccmb.res.in[/url]

further queries in this topic are always welcome.
wishes,
abhay
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