Sequence analysis under selective pressure at variable positions in chimera enzymes.

<p>Amino acids are represented by the one code letter. The histograms represent the relative frequencies of the selected versus unselected libraries. The red colored histograms (*) represent those amino acids at the variable positions that had a frequency either significantly higher (2 standard deviations) or lower than expected by chance. The sequence analysis for the α-helix 3 and β-strand 7 from MetR swapped into the TrpF scaffold are shown in A and B, respectively. The variable positions are represented by the NNS codon. The three-dimensional structure of the <i>E. coli</i> enzyme (PDB: 1PII) was used to identify the variable positions. The amino acid numbering of TrpF is according to gene reported in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0070582#pone.0070582-OchoaLeyva1" target="_blank">[25]</a>.