Structural Studies of Pterin-Based Inhibitors of Dihydropteroate Synthase

Abstract

Dihydropteroate synthase (DHPS) is a key enzyme in bacterial folate synthesis and the target of the sulfonamide class of antibacterials. Resistance and toxicities associated with sulfonamides have led to a decrease in their clinical use. Compounds that bind to the pterin binding site of DHPS, as opposed to the p-amino benzoic acid (pABA) binding site targeted by the sulfonamide agents, are anticipated to bypass sulfonamide resistance. To identify such inhibitors and map the pterin binding pocket, we have performed virtual screening, synthetic, and structural studies using Bacillus anthracis DHPS. Several compounds with inhibitory activity have been identified, and crystal structures have been determined that show how the compounds engage the pterin site. The structural studies identify the key binding elements and have been used to generate a structure-activity based pharmacophore map that will facilitate the development of the next generation of DHPS inhibitors which specifically target the pterin site.

The identification, analysis and structure-based development of novel inhibitors of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase

“…The EcHPPK-GST fusion enzyme was expressed in E.coli and purified as previously described in three steps: (1) GSTrap FF column (Amersham Biosciences), (2) thrombin digestion to remove the GST tag, and (3) size exclusion chromatography. 27, 33 …”

Replacing Sulfa Drugs with Novel Dhps Inhibitors

“…It engages the pterin-binding pocket in a similar fashion to the substrate analogs 6-hydroxymethyl-pterine-pyrophosphate and 6-hydroxymethyl-pterine-monophosphate (Figure 5C), and interacts with five out of the six pterin-binding residues [29]. In a later study, the close analog 6-amino-5-nitrosoisocytosine was shown to be a more potent inhibitor of Ba DHPS, and this result was rationalized by the crystal structure which revealed that the free amine binds to Asp101 via an electrostatic/ hydrogen bond interaction [30]. In the previous study by Lever and co-workers [41], substituting the nitroso moiety for a nitro group resulted in a slightly decreased affinity to the enzyme, and this result is supported by the crystal structures of compounds 10 & 13 [30].…”

Biosynthesis of Isoprenoids: Crystal Structure of the [4Fe–4S] Cluster Protein IspG

“…This domain is yet another member of the large TIM-barrel superfamily. 24 A DALI search 25 showed the highest degree of similarity with dihydropteroate synthase 26 from Bacillus anthracis (Research Collaboratory for Structural Bioinformatics accession code 3H2M; rmsd = 1.9 Å with a matching rate of 57%, Fig. 2 and Fig.…”