Hidden symmetries in primary sequences of small alpha proteins

Proteins have regular tertiary structures but irregular amino acid sequences. This made it very difficult to decode the structural information in the protein sequences. Here we demonstrate that many small alpha protein domains have hidden sequence symmetries characteristic of their pseudo-symmetric tertiary structures. We also present a modified method of recurrent plot to reveal this kind of the hidden sequence symmetry. The results may enable us understand parts of the relations between protein sequences and their tertiary structures, i.e, how the primary sequence of a protein determines its tertiary structure.