Front Cover: Human Cellular Retinol Binding Protein II Forms a Domain‐Swapped Trimer Representing a Novel Fold and a New Template for Protein Engineering (ChemBioChem 22/2020)

The folding pathway of human cellular retinol binding protein II was manipulated to favor formation of the shown domain‐swapped trimer, by rational protein engineering of a cross‐subunit disulfide bond. The inset shows the zinc binding site, engineered into the trimer with a single mutation, by exploiting the threefold axis of symmetry in the center of the trimer. The “purple flag” iris shows how the overall threefold symmetry positions the small, white inner petals, reflective of the three coordinating histidines in the trimer. More information can be found in the communication by J. H. Geiger et al.