The external aldimine form of the mutant beta-S377A Salmonella thypi tryptophan synthase in open conformation showing dual side chain conformations for the residue beta-Q114, sodium ion at the metal coordination site, and F9 inhibitor at the alpha-site. One of the beta-Q114 rotamer conformations allows a hydrogen bond to form with the PLP oxygen at the position 3 in the ring
