[BiO BB] protein clustering threshold

[Shamshad Zarina]

Crystallins are very good examples for proteins having
structural and sequence similarity but different
functions. I work on lens protiens but I don't recall
an example with >90% identity yet different functions.


One example with less identity is of Rho-crystallin
found in bull-frog where it acts as 'structural
protein' to maintain lens transparency. It shows 55%
sequence identity with Aldo-keto reductase superfamily
which are enzymes. Both proteins have similar three
dimensioanl structure and one residue required for
catalytic activity is absent in rho-crystallin.

Best,
Shamshad 

--- Iddo Friedberg <idoerg at burnham.org> wrote:
> Not to answer your question directly, 
> just to add confusion:
> 
> How about the same protein which performs different
> functions?
> Crystallins
> are an example of a protease which, in the eye lens,
> serves as a
> transparent buffer.
> 
> There are other such "moonlighting proteins" look
> at:
>
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12902157&dopt=Abstract
> 
> ./I
> 
> --
> Iddo Friedberg, Ph.D.
> The Burnham Institute
> 10901 N. Torrey Pines Rd.
> La Jolla, CA 92037, USA
> Tel: +1 (858) 646 3100 x3516
> Fax: +1 (858) 646 3171
> http://ffas.ljcrf.edu/~iddo
> 
> On Fri, 6 Feb 2004, Hongyu Zhang wrote:
> 
> > Does anyone have examples of two proteins with
> >90%
> > identity have differenct functions? I need it as a
> > proof to cluster a protein sequence library.
> > 
> > Thanks!
> > 
> > Hongyu
> > 
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