Amino acid characteristics in protein native state structures

We present a geometrical analysis of the protrusion statistics of side chains in more than 4,000 high-resolution protein structures. We find that when the amino acids are grouped based on chemical similarity, the resulting groups equally well fit the geometrical attributes in a harmonious manner. Our analysis underscores the role of minimal frustration in the evolution of protein sequences that fit within a pre-sculpted menu of putative native state folds.