Overall crystal structure of PhKAT in complex with PLP and 2OG as a substrate and allosteric effector (PDB code: 3ATH).

(A) Surface and cartoon representation of the structure of functional PhKAT dimer bound with 2 PLP cofactors and 4 2OGs. A Cα trace is shown with blue and green coloring with 2 subunit chains. Black arrows indicate the position of PLP as cofactor and 2OG as substrate and allosteric effector. Left hand, cartoon-and-surface representation of the allosteric–effector complex. Right hand, cut-away of the overall structure of the left-hand complex. (B), (C) Part of 2OG as a substrate (B) and as an allosteric effector (C) with a 2F_o-F_c electron density map contoured at 1.3 σ. (D), (E), (F) Superimposed representation of 2OG complex structures of PhKAT. (D) Cartoon representations of 2OG complex structures of PhKAT after optimal superimposition. 2OG as a substrate complex (PDB code: 3AOW) and 2OG as a substrate and an allosteric effector complex (PDB code: 3ATH). Gray cartoon-and-line represents PhKAT bound only to 2OG as a substrate complex; PhKAT bound to 2OG as substrates and allosteric effectors is colored green and blue for 2 subunits. Yellow circles show regions with significant conformation changes. Black arrows indicate the position of 2OG as substrates and allosteric effectors. (E), (F) Stick-and-line representation of the PLP-cofactor binding sites and 2OG as substrate after optimal superposition of the 2 PhKAT complex structures. 2OG as a substrate complex only is colored gray. (E) Black and gray labels, and dotted lines show the distance (Å) between 2OG and the C4A atom of PLP in a Schiff-base link with lysine-269. (F) Angles (°) of 2OG between substrate-bound PhKAT, and substrate- and allosteric effector-bound PhKAT structures. The figure was generated using PyMOL.