Structural comparison between N-terminal regions.

(A-H) Single-subunit structures from homodimeric enzymes are represented and colored as done in Fig 1A. (F) For the type VI enzyme, an additional C-terminal helix was represented in orange. The representative structures for each type are as follows: SpAST for type I; PLP-dependent acyl-CoA synthase (PDB code, 1BS0) for type II; GABA-dependent transcriptional activator of gabT (PDB code, 4MGR) for type III; cystalysin (PDB code, 1C7N) for type IV; L-threonine-O-3-phosphate decarboxylase (PDB code, 1LC5) for type V; sphingosine-1-phosphate lyase (PDB code, 5K1R) for type VI; L-tyrosine decarboxylase MfnA (PDB code, 3F9T) for type VII; Tryptophan decarboxylase (PDB code, 4OBU) for type VIII.