Figure 4.

Alignment of the amino acid sequences ofE. coliandB. subtilisPRPP amidotransferases. The amino acids were shown in single-letter code. Identical residues were shaded and conserved residues were in box. Symbols α and β represented the secondary structure elements for two proteins. The amino acid residues in the box referred to the conservative replacement of amino acid residues. The alignment was performed with the program ESPript 3.0. Residues replaced by site-directed mutagenesis were marked with a closed triangle. Bsu_BSU06490, B. subtilis PRPP amidotransferases; eco_b2312, E. coli PRPP amidotransferases.