Figure 2

Directed evolution reveals non-traditional substitutions of transmembrane Trps. Distribution of amino acid substitutions that successfully mated found for the outer Trp block mutants (top), and for the inner Trp block mutants (bottom). Amino acid frequencies were calculated from a total of 102 mutants (72 unique mutants) that successfully mated and showed resistance to doxorubicin and FK506. Amino acids occurring at a frequency of >10% were color coded according to the Zappo scheme116.