It does seem to be true that proteins of a given kind do evolve at a surprisingly, although not exactly, uniform rate.

In contrast, other proteins have evolved to bind to particular DNA sequences.

These proteins have evolved to recognize and bind the transition state of peptide hydrolysis reaction which is a tetrahedral intermediate.

Any such protein has evolved for some tasks, but may contain molecular nooks and crannies that can serve as novel catalytic sites.

Some proteins have evolved to recognize only one base-pair type, and use intermolecular interactions to shift the equilibrium between the two geometries.

He is known for resurrecting ancestral genes and tracing the mechanisms by which proteins evolve new functions.

Or the proteins may be in the same species, but have evolved from a single protein whose gene was duplicated in the genome (paralogy).

Thus, the issue of whether fungal proteins are diseases, or have evolved for some specific functions, still remains unresolved.

However there is no universally agreed upon theory that explains why proteins with multiple roles evolved.

It is quite possible the protein evolved to play some role other than making people itch and their eyes water.