Sequence Comparison of the In Vitro Selected Proteins.^a

aSequences of the Family B proteins from different points in the evolution history of this non-biological protein. Primordial and R18 consensus refer to the consensus sequences from rounds 8 and 18, respectively, in the original ATP-binding selection. Protein 18-19 was the highest affinity clone isolated from round 18. Protein DX is the double-mutant protein isolated by optimizing protein 18-19 for improved folding stability. The N32D mutation was present in 35 out 53 sequences. The D65V mutation was present in 45 out of 53 sequences. Other selected mutations were present ≥ 5 out of 53 sequences.