  In protein folding the term plasticity refers to the number of alternative
folding pathways encountered in response to free energy perturbations such as
those induced by mutation. Here we explore the relation between folding
plasticity and a gross, generic feature of the native geometry, namely, the
relative number of local and non-local native contacts. The results from our
study, which is based on Monte Carlo simulations of simple lattice proteins,
show that folding to a structure that is rich in local contacts is considerably
more plastic than folding to a native geometry characterized by having a very
large number of long-range contacts (i.e., contacts between amino acids that
are separated by more than 12 units of backbone distance). The smaller folding
plasticity of `non-local' native geometries is probably a direct consequence of
their higher folding cooperativity that renders the folding reaction more
robust against single- and multiple-point mutations.
