  In order to extend the results obtained with minimal lattice models to more
realistic systems, we study a model where proteins are described as a chain of
20 kinds of structureless amino acids moving in a continuum space and
interacting through a contact potential controlled by a 20x20 quenched random
matrix. The goal of the present work is to design and characterize amino acid
sequences folding to the SH3 conformation, a 60-residues recognition domain
common to many regulatory proteins. We show that a number of sequences can
fold, starting from a random conformation, to within a distance root mean
square deviation (dRMSD) of 2.6A from the native state. Good folders are those
sequences displaying in the native conformation an energy lower than a
sequence--independent threshold energy.
