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<DIV>Proteins are polypeptides. Peptides are short chains of amino acids. Just
how long can a peptide be before it should be called a protein? I'm not going to
stick my neck out a give a number, but one thing is clear: 2 amino acids does
not a protein make.</DIV>
<DIV> </DIV>
<DIV>Andrew</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>===============================================================<BR>Andrew
Mitchell<BR>Senior Lecturer, Molecular Phylogenetics<BR>School of Molecular and
Cellular Biosciences<BR>University of Natal<BR>Private Bag X01<BR>Scottsville,
3209<BR>SOUTH AFRICA</DIV>
<DIV> </DIV>
<DIV>Tel: +27 (0)33 260 5815<BR>Fax: +27 (0)33 260 5462</DIV>
<DIV> </DIV>
<DIV><A
href="http://www.nu.ac.za/department/members/members.asp?dept=bioscienunp&id=123456">http://www.nu.ac.za/department/members/members.asp?dept=bioscienunp&id=123456</A><BR></DIV>
<DIV><BR>>>> bio_bulletin_board-request@bioinformatics.org 02/02/21
07:02:18 >>><BR>Message: 1<BR>Date: Wed, 20 Feb 2002 13:15:45
-0500<BR>From: hinaishadh@netscape.net<BR>To:
bio_bulletin_board@bioinformatics.org<BR>Subject: [BiO BB] Definition of a
protein<BR>Reply-To: bio_bulletin_board@bioinformatics.org<BR><BR>Hi Kiran,<BR>I
am sure I will get a lot of flake for this BUT<BR>Amino acids are building
blocks of protein. In other words proteins are polymers of amino
acids. How many? By definition 2 or more should do.<BR><BR>That said, keep
in mind that earlier biochemical scientists did not know the nature of the
molecule thay were working on. So, the names like toxins, or even "active
principle" in the ddays of Pasteur and Robert Koch (1870s!). To further
complicate matters you have glycoproteins that are mainly proteins with sugar
side chains, and peptidoglycans that have small peptide backbone but really
long, branched sugars chains (generally constituting 90% of the mol. wt. of the
whole molecule).<BR><BR>LOts of work was done using precipitation as one way to
isolate large biological molecules. So the growth factors and small peptides
that were soluble by such criteria were not called proteins but peptides or
peptide hormones etc.<BR><BR>Hope this helps<BR><BR>Naishadh Desai<BR>Perlegen
Sciences<BR>Mountain View, CA 94043<BR><BR><BR>><BR>>Message:
3<BR>>Date: Wed, 20 Feb 2002 02:48:00 -0800 (PST)<BR>>From: Ayyagari Kiran
<kiran_ayyagari@yahoo.com><BR>>To:
bio_bulletin_board@bioinformatics.org<BR>>Subject: [BiO BB] what is the
minimum length of protein? and why differentiate protein &
peptides<BR>>Reply-To:
bio_bulletin_board@bioinformatics.org<BR>><BR>>hi,<BR>>1)what is the
minimu length of A protein ?<BR>>(please mention the minimal possible
length of<BR>>protein, its minimal mol wt(in kDa) and also types
of<BR>>proteins by example.<BR>><BR>>2) is it that a biomolecule can be
called as a protein<BR>>based on its structural organization (like if
domains<BR>>are present)<BR>>or <BR>>is it that a biomolecule can be
called as protein<BR>>based on Functional implications??like example can
be<BR>>toxin of 55 amino acids causes raise in antibodies<BR>>production.
why is it not called a protein and why it<BR>>is called a peptide toxin
despite having amino acids.<BR>> <BR>>thanks in
advance<BR>><BR>>A.S.Kiran<BR>><BR></DIV></BODY></HTML>