smallest working peptide

[kukua]

Hi,
I have question, that might seem naive for many of you, but I cannot find direct answer anywhere: what is the smallest known WORKING natural peptide? I mean working on its own, not being part of some bigger aggregation.
I am mainly interested in smallest ionophoric peptides, but I would be grateful for any information about other smallest peptides (should I say "proteins"? when we go below few dozen amino acids it probably is not even a peptide anymore... ;-)
best,
kika.

[kanzure]

whatislife com/reader/motion/motion.html

This page suggests that the smallest one might be 15 units long. I am sure that there are even smaller ones out there. Have you tried the protein databases from the U.S. government and National Institute of Health? Or the ones provided from universities?

- Bryan

[musgun]

There are the integrin binding RGDs. You can have pentapeptides that will have a HUGE effect on cell behaviour.
I also work with as short as heptapeptides with different functions but they are not natural I designed them.