There are something like 10^94 different
>permutations of the cytochrome c molecule that will function just fine and
>dandy in your body. (see Hubert Yockey, Information Theory and Molecular
>Biology, p. 59). There are a total of 10^137 possible permutations of a
>sequence that long. So, yes there are limits, but they aren't very limiting.
That figure you use of 10^94. We don't know that these will function just
fine (to say nothing of dandy) at all. We only know of a few thousand that
will function just fine in specific organisms and one or a handful that
will function just fine in man. The others are just hypothetically
conceivable, but untested. Probably most would not work in man, So your
point is weak.