Figure 4.

Single missense mutants of Le-ACS2 and their phenotypes. The amino acid sequence of wild-type Le-ACS2 is shown. Residues in bold are conserved in at least 75% of the aligned sequences of ACC synthase. The single amino acid substitutions are listed under the residue of Le-ACS2 that has been mutated and are shown in red for class I mutants, green for class II mutants, and orange for class III mutants. Numbers below the substituted residue indicate the number of independent clones isolated. The predicted secondary structure and solvent accessibility of the amino acid residues is shown above the amino acid sequence. The symbols used are #, helix; o, β-strand; and b, buried or with less than 10% solvent accessibility. The conserved residues between ACC synthase and subgroup 1 aminotransferases and the four invariant residues in all aminotransferases are indicated by ★ and ⊛, respectively. The ▾ shows the demarcation between the regions of Le-ACS2 subjected to PCR random mutagenesis. See Materials and Methods.