Evolutionary markers in the (beta/alpha)8-barrel fold.

Enzymes with the (beta/alpha)(8)-barrel fold are involved in the catalysis of a wide variety of biochemical reactions. The active sites of these enzymes are located on the C-terminal face of the central beta-barrel. Conserved amino acid sequence, as well as secondary, tertiary and quaternary structure patterns are providing a rich body of data to support the premise of a common ancestry of many members of the (beta/alpha)(8)-barrel fold family of enzymes. Recent data indicate that there is at least one example of a bienzyme that functions as an ammonia channel, adding a new level of functional diversity to the (beta/alpha)(8)-barrel fold. These proteins have become ideal tools that can be used in conjunction with directed evolution techniques to engineer novel catalytic activities.