3GBR

Anthranilate phosphoribosyl-transferase (TRPD) double mutant D83G F149S from S. solfataricus

Summary for 3GBR

• Entry DOI: 10.2210/pdb3gbr/pdb
• Related: 1GXB 1O17 2GVQ
• Descriptor: Anthranilate phosphoribosyltransferase, 1-O-pyrophosphono-5-O-phosphono-alpha-D-ribofuranose, MANGANESE (II) ION, ... (6 entities in total)
• Functional Keywords: transferase, amino-acid biosynthesis, aromatic amino acid biosynthesis, glycosyltransferase, tryptophan biosynthesis
• Biological source: Sulfolobus solfataricus
• Total number of polymer chains: 2
• Total formula weight: 76399.09

Authors

Bruning, M.,Schlee, S.,Deuss, M.,Ivens, A.,Mayans, O.,Sterner, R. (deposition date: 2009-02-20, release date: 2009-12-15, Last modification date: 2023-11-01)

Primary citation

Schlee, S.,Deuss, M.,Bruning, M.,Ivens, A.,Schwab, T.,Hellmann, N.,Mayans, O.,Sterner, R.
Activation of anthranilate phosphoribosyltransferase from Sulfolobus solfataricus by removal of magnesium inhibition and acceleration of product release
Biochemistry, 48:5199-5209, 2009

PubMed Abstract: Anthranilate phosphoribosyltransferase from the hyperthermophilic archaeon Sulfolobus solfataricus (ssAnPRT) is encoded by the sstrpD gene and catalyzes the reaction of anthranilate (AA) with a complex of Mg(2+) and 5'-phosphoribosyl-alpha1-pyrophosphate (Mg.PRPP) to N-(5'-phosphoribosyl)-anthranilate (PRA) and pyrophosphate (PP(i)) within tryptophan biosynthesis. The ssAnPRT enzyme is highly thermostable (half-life at 85 degrees C = 35 min) but only marginally active at ambient temperatures (turnover number at 37 degrees C = 0.33 s(-1)). To understand the reason for the poor catalytic proficiency of ssAnPRT, we have isolated from an sstrpD library the activated ssAnPRT-D83G + F149S double mutant by metabolic complementation of an auxotrophic Escherichia coli strain. Whereas the activity of purified wild-type ssAnPRT is strongly reduced in the presence of high concentrations of Mg(2+) ions, this inhibition is no longer observed in the double mutant and the ssAnPRT-D83G single mutant. The comparison of the crystal structures of activated and wild-type ssAnPRT shows that the D83G mutation alters the binding mode of the substrate Mg.PRPP. Analysis of PRPP and Mg(2+)-dependent enzymatic activity indicates that this leads to a decreased affinity for a second Mg(2+) ion and thus reduces the concentration of enzymes with the inhibitory Mg(2).PRPP complex bound to the active site. Moreover, the turnover number of the double mutant ssAnPRT-D83G + F149S is elevated 40-fold compared to the wild-type enzyme, which can be attributed to an accelerated release of the product PRA. This effect appears to be mainly caused by an increased conformational flexibility induced by the F149S mutation, a hypothesis which is supported by the reduced thermal stability of the ssAnPRT-F149S single mutant.

PubMed: 19385665
DOI: 10.1021/bi802335s

Experimental method

X-RAY DIFFRACTION (2.25 Å)