sequence's ends -- crucial to protein folding too?
Frank Küster geb. Fürst
ffrank at rz.uni-potsdam.de
Sat Sep 21 12:17:22 EST 2002
"Artem Evdokimov" <AEVDOKIMOZ at cinci.rr.com> schrieb:
> > You're right. Things are always more complicated if you look closer. One
> > other example, kind of extreme, comes to my mind: Pro-domain assisted
> > folding, e.g. in alpha-lytic protease, which is less stable than the
> > unfolded form after the pro-domain has been cleaved.
> Let's not forget concanavalin A which is expressed as a chain that undergoes
> cleavage and re-ligation with a large piece turned around :)
Is it turned around? I never had close look at the sequence or the
strucutre. But in the legume lectin reviews I read (and I read a couple
in the last months), they always say that it is circularly
permuted. That would mean that there is no change in the structure, only
the old termini are re-ligated and the new ones are free. The original
termini are very close to each other in the legume lectin monomer
(separated just by a "non-existing" beta-turn).
I think nobody knows which effect this procedure has on ConA folding,
because it folds first, and I am not aware of any in vitro study on ConA
folding. There are unfolding studies, mainly from the Surolia group,
that use scanning calorimetry and urea (or guanidinium?) unfolding. But
in the DSC case, it is controversial if their interpretation is right
(see Marcos, ..., Shnyrov 1999 in FEBS Lett). And as for the denaturant
induced stuff, I strongly believe they only watched unfolding kinetics,
not an unfolding equilibrium. Therefore, their quantitative
interpretation is at least questionable.
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