structure

D.K. dk at no.email.thankstospam.net
Mon Jan 7 11:10:57 EST 2002


ffrank at rz.uni-potsdam.de (Frank =?iso-8859-1?q?F=FCrst?=) wrote:
>dk at no.email.thankstospam.net (D.K.) schrieb:
>
>> Also, at 
>> least some folds, if not most, appear to fold not into global free energy 
>> minimum. I worked with several proteins that fold spontaneously in 
>> solution into something that has seemingly nothing to do with their 
>> native folds.
>
>Can you give some references? 

Nope.

>You don't mean folding intermediates, do
>you? 

Don't know :-) They may be folding intermediates in some sense,
but if they are stable and never reach native fold, I'd call them
mistfolded. 

>Of course there are proteins with differently folded states, but I
>don't recall a case where I'd say that one has "nothing to do" with the
>native state - if it's not a (possibly aggregation-prone) misfolded
>folding intermediate: Probably a case for a chaperone, and thus a local
>minimum itself.

Nothing to do would not be a statement I make in a publication
with the amount of data I have (never even attempted to study
thing things) :-). Still: 

Phosphatidylinositol-4-phosphate 5-kinases type Igamma.  
Expressed in E coli in inclusion bodies, solubilized in urea,
dialyzed against buffer - 100% soluble, ~ monomer by gel
filtration, zero enzymatic activity. Don't think it is the case
of posttranslational modification because the only one known
is phosphorylation. Complete dephosphorylation  of native 
enzyme only moderately reduces activity, phosphorylation of
"renatured" enzyme fails to activate it. 

Actin. Almost same as above. Inclusion bodies are 
much more difficult to solubilize. After dialysis, protein is 
100% soluble, does not polymerize, does not bind ATP,
does not bind gelsolin. Did not do gel filtration in this case. 
Actin result is even less surprising as there is a speciat 
chaperonin that folds it and tubulin (TRiC/CTT) and - 
shockingly - I can't get native actin even when it is 
overexpressed in baculovirus system (product is insoluble 
and behaves as one made in E.coli). 

DK




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