Overall structure of SpAST.

(A) The homodimeric crystal structure of SpAST. The small domains (green and blue), large domains (light green and cyan), and N-terminal arms (hot pink) are presented. The phosphates in the active site and glycerol molecules are represented as yellow stick. The active sites are highlighted as dashed red circles. (B) Pi interactions at the subunit interface. Pairs of tyrosine residues, namely Y298–Y298 at helix α2 as well as Y70–Y298 at loop α2–α3 and helix α11, respectively, are represented as yellow stick. (C) Two monomers of the homodimeric structure are represented in the same orientation and color as given in Fig 1A. 2mFo-DFc map for the (D) phosphate as well as for the (E) glycerol molecule. (F) The chemical structures of pyridoxal 5ʹ-phosphate is shown.