Allosteric inhibitor specificity of Thermotoga maritima 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase

Abstract

3-Deoxy-D-arabino-heptulosonate 7-phosphate synthase (DAH7PS) catalyses the first step of the shikimate pathway for the biosynthesis of aromatic amino acids. Allosteric regulation of Thermotoga maritima DAH7PS is mediated by L-Tyr binding to a discrete ACT regulatory domain appended to a core catalytic (β/α)8 barrel. Variants of T. maritima DAH7PS (TmaDAH7PS) were created to probe the role of key residues in inhibitor selection. Substitution Ser31Gly severely reduced inhibition by L-Tyr. In contrast both L-Tyr and L-Phe inhibited the TmaHis29Ala variant, while the variant where Ser31 and His29 were interchanged (His29Ser/Ser31His), was inhibited to a greater extent by L-Phe than L-Tyr. These studies highlight the role and importance of His29 and Ser31 for determining both inhibitory ligand selectivity and the potency of allosteric response by TmaDAH7PS.

Keywords: 1,3-bis[tris(hydroxymethyl)methylamino]propane; 3-deoxy-d-arabino-heptulosonate 7-phosphate; 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase; ACT domain; Allosteric regulation; BTP; DAH7P; DAH7PS; DAHPS; E4P; PDB; PEG; SAXS; Shikimate pathway; d-erythrose 4-phosphate; polyethylene glycol; protein data bank; small angle X-ray scattering.