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On Thu, 22 Sep 2005, Savvas N. Savvides wrote:

> In that paper you will also find a plot of r.m.s.d vs sequence identity
> which reveals that the 3 angs rmsd (which we generally take as an
> upper-boundary for structural similarity) occurs at about 25-30% seq.id.
>  
> Best wishes
> Savvas
> 
 
-I dont think this true a) personally i know explames -at least 
beta-propellers with seq id less than 15% and rmsd around 2 A, 
and i am sure many more.
b) If you check the EMBO J Chothia paper (cant find it now, but
the same data is in Creightons book) you see rmsd 2 A occurs below
20% identity. 

The other question is what do you mean by structural
similarity? surely proteins can have the same fold wihtout 
practically any >20% seq. identity ---if this about feasibility
of use as a molecular replacement, but thats another thing.

Tommi


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