Are there any (documented :-) ) examples of nature (rather than genetic
engineers) deleting some internal portion of a protein coding sequence and
thus creating a new protein with a new structure and function?
I'm asking this because, in the process of studying a family of plant
proteins, we find two entries in the database that clearly align with the
family at their N and C terminal regions but are missing a large section in
the middle. The core globular structure (the 3-D structure of one of the
family members is known) is normally about 100 aas long and in these two
'abridged' sequences an internal chunk of 40 aas has been removed. In
removing those amino acids one loses two beta strands which are essential to
the known folded structure.
The two 'abridged' sequences (from cDNAs expressed in two different plants)
while similar, have diverged enough from their common ancestor that one
_might_ postulate that there's some selective pressure to keep them expressed.
So, we're back to the original question. One way that nature might create a
new protein (yes, I'm anthropomorphizing here) is to delete an internal
portion of a coding sequence and let the new 'abridged' polypeptide chain fold
in a new way. Are there any examples of this?
Thanks in advance,
Liz Greene
