Question

Why can’t proteins have mirror symmetry?

Short answer

Proteins cannot have mirror symmetry because the conversion of chiral L residues to chiral D residues takes place during the association of the subunits.

Step-by-step solution

Symmetrical arrangement of protein subunits

In an oligomeric protein, the subunits are symmetrically arranged, where each subunit monomer acquires a geometrically equivalent position in the oligomer.

Symmetry of the oligomeric protein

The oligomeric protein brings the subunits into coincidence. Chiral L residues are converted to chiral D residues to make that happen. Because of this conversion, the proteins cannot have mirror symmetry.