Finally, the internal and quaternary symmetries can be combined to obtain the global

overall combined symmetry. As we have seen before, the protein 1VYM is a DNA-clamp that

has three chains relates by C3 symmetry. Each chain is internally C2 symmetric, and each

part of the C2 internal symmetry is C2 symmetric, so a case of **hierarchical symmetry**

(C2 + C2). Once we have divided the whole structure into its asymmetric parts, we can

analyze the global symmetry that related each one of them. The interesting result is that

in some cases, the internal symmetry **multiplies** the point group of the quaternary symmetry.

What seemed a C3 + C2 + C2 is combined into a D6 overall symmetry, as we can see in the figure

below:

This results can gives hints about the function and evolution of proteins and biological

structures.