Pleas Help Quick

Hiranya S. Roychowdhury hroychow at
Fri May 5 10:15:00 EST 2000

Proteins are more complex than just their sum of amino acids. Whether one
retains its functionality by just having one or a few aa's altered depends
on a lot of different factors: 1. physicochemical property of the target aa;
2. location of the aa in the polypeptide (IOW, the secondary structure of
the region, eg H,C or E); 3. neighboring aa's; 4. its functional
significance in the tert. structure of the prot., etc.

When you change the aa's of a protein, say "A", "significantly", chances are
that the resultant protein will no longer be "A". The functionality of a
protein depends generally on some select group of aa within the core. It is
possible to have "similar" catalytic or prosthetic properties in a grossly
altered protein, and that is not uncommon, evolutionarily speaking. For
example, there are numerous kinases that have about 25% aa identities among
themselves. This reflects the variability in substrates. Similarly, check
the structures of hemoglobin and leghemoglobin and you may have some answers
to your question. I think the LgHgb may be in PDB.

At 02:38 AM 5/5/00 +0100, Toby Skinner wrote:
>Hello, I have a simlpe question and I really nead an answer quick.
>Any protein is made up of amino-acids, it is these that define the overall
>structure and therefore function of the protein.  I know that amino-acids
>can be replaced by other amino-acids without effecting the function of the
>So if I was able to generate a new say, Haemoglobin protein which has a
>significantly different amino-acid content, does anyone know if (in theory)
>it could be created in the lab and experimented apon?  This is a serious
>question and has implications for some software I have written
>(dissertation) for finding amino-acid sequences which fold into the same
>user specified protein.  The idea is that a useful but toxic protein could
>be enginered in the lab to be non-toxic.
>Any thanks is very appreciated.

Dr. Hiranya Sankar Roychowdhury
New Mexico State University
Las Cruces, NM 88003
Ph. (505) 646-5785
hroychow at


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