Structural similarity between native proteins and chimera constructs obtained by inverting the amino Acid sequence.

The analysis of the symmetry of protein three-dimensional structures can be extremely useful in order to understand and classify the protein structural universe. The structures of proteins with back-traced amino acid sequence were modeled and compared to the structures of their native counterparts. Only in a very limited set of cases, the two objects showed a significant level of similarity. These extremely symmetric examples can be of any structural class and of any dimension. The lack of biunique "N to C" and "C to N" symmetry at the structural level mirrors that at the sequence level and we propose to design as a dlof symmetry the cases in which a protein structure is similar to its back-traced variant.