Evolution and Protein Folds

Ram Samudrala ram at mbisgi.umd.edu
Fri Jun 24 06:22:54 EST 1994


Suppose we have a gene duplication.  One copy of the gene stays
mutationally put as there is selective pressure for the protein it
produces.  The other copy is free to accumulate mutations and perhaps
evolve to a new function.

Now, all the books I've read talk about evolution in terms of protein
function.  That is, there is selection as soon as the mutation gene
produces a protein that has some function.  What I am interested in
knowing is if there is any model that speaks of evolution in terms of
protein structure.

I am interested in knowing this because I find it hard to believe that
/any/ mutation will be tolerated in the gene while it is drifting and
there's no selection for function.  I believe that only
genes/mutations that conserve the protein fold would be selected for.
I say this because if you have an existing fold and you make mutations
that destroy the fold, then it would be incredibly hard (intiutively,
it seems like it would take longer by several orders of magnitude) for
the mutations to be undone to restore the fold.

If there is some preservation of protein structure between
generations, how exactly is this accomplished?  

I am also told that there is evidence of "genes" that produce proteins
that misfold.  If this is true, how can be explained in terms of
evolution/natural selection.  If you think this is false, why?

--Ram

ram at elan1.carb.nist.gov   The suburbs are when they cut down all the
                          trees and then name the streets after them!
                                                   ---Alfred E Neuman



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