sequence's ends -- crucial to protein folding too?

Frank Fürst ffrank at rz.uni-potsdam.de
Wed Sep 18 03:06:48 EST 2002


"Adrian" <AdrnLgrvtn at gazeta.pl> schrieb:

> Have all positions along an amino acid sequence the potential to influence
> the folding equally importantly? Specificly, I wonder if amino acids
> positioned near both ends of a sequence could be crucial to how 3d-structure
> would look like? Whats more, will removing 1 or 2 aminoacids from a
> sequence's end (shortening) make any difference?

I don't know wether a general answer can be given, but frequently the
terminal residues are disordered in X-ray-structures (in NMR even more,
I think). Furthermore, it is usually possible to fuse a tag (e.g. a
6-His-tag) to any of the termini, or even to fuse a whole protein via a
linker sequence.

This means that the terminal residues are less important than others. It
might be a consequence of their having less possibility to make
near-in-sequence contacts, or (just an idea) fixing terminal residues
might have a higher entropic cost than fixing internal ones.

However, I think there are a few examples where the termini are not
located at the periphery of the structure, but rather inside. I don't
remember a particular protein, and I don't have time to look it up.

Bye, Frank
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