Versatility, stability, and evolution of the (βα)8-barrel enzyme fold

The canonical (βα)8-barrel also known as TIM barrel, contains about 200 amino acids and is composed of eight units consisting of a β-strand and an α-helix that are connected by βα-loop. Structures of sample barrels were analyzed which determines the (βα)8-barrel's stability. Residues were assumed to be important for stability depending on their involvement in long-range interactions, the hydrophobicity of the environment and its conservation. To maintain the stability of the (βα)8-barrel fold, about 180 out of the 250 sequence positions within yeast TIM were randomized using combinatorial mutagenesis. The (βα)8-barrel is catalytically versatile, and harbors active sites with high functional and structural plasticity which makes it an ideal scaffold for the design of new catalytic activities, either by rational design or by directed laboratory evolution.