An aminoquinazoline inhibitor of the essential bacterial cell wall synthetic enzyme GlmU has a unique non-protein-kinase-like binding mode

Abstract

GlmU is a bifunctional enzyme with acetyltransferase and uridyltransferase activities, and is essential for the biosynthesis of the bacterial cell wall. Inhibition results in a loss of cell viability. GlmU is therefore considered a potential target for novel antibacterial agents. A HTS (high-throughput screen) identified a series of aminoquinazolines with submicromolar potency against the uridyltransferase reaction. Biochemical and biophysical characterization showed competition with UTP binding. We determined the crystal structure of a representative aminoquinazoline bound to the Haemophilus influenzae isoenzyme at a resolution of 2.0 Å. The inhibitor occupies part of the UTP site, skirts the outer perimeter of the GlcNAc1-P (N-acetylglucosamine-1-phosphate) pocket and anchors a hydrophobic moiety into a lipophilic pocket. Our SAR (structure-activity relationship) analysis shows that all of these interactions are essential for inhibitory activity in this series. The crystal structure suggests that the compound would block binding of UTP and lock GlmU in an apo-enzyme-like conformation, thus interfering with its enzymatic activity. Our lead generation effort provides ample scope for further optimization of these compounds for antibacterial drug discovery.

"Molecular mechanisms adopted by abiotic stress tolerant Pseudomonas fluorescens (NBAII-PFDWD) in response to in vitro osmotic stress"

“…GlmU is a precursor for bacterial cell wall synthesis components like lipopolysaccharides and peptidoglycan. Inhibition of GlmU adversly affects cell viability (Larsen et al, 2012). Hence, this has been utilized as target for antibiotic drug discovery (Mochalkin et al, 2007).…”

Biosynthesis of uridine diphosphate N‐Acetylglucosamine: An underexploited pathway in the search for novel antibiotics?

“…79,[104][105][106] These series of inhibitors are predicted to bind within the hydrophobic pocket, occupying part of the UTP-binding site and locking GlmU in an apo-enzyme-like conformation. 79,[104][105][106] Two of the inhibitors (Compounds 80-81) demonstrate significant whole cell activity against M. tuberculosis (MICs = 6.25-25 μM) and a lack of toxicity in mammalian Vero cell lines, indicating that aminoquinazoline inhibitors hold potential as antibiotic candidates. 106 In silico high throughput screening has been used to identify five structures (Compounds 82-86) that are predicted to be selective for the bacterial enzyme with binding to the eukaryotic enzymes expected to be hindered by pocket residues in AGX1/AGX2; however, these leads have yet to be examined for in vitro activity (Figure 13).…”

“…High throughput screening has identified multiple series of inhibitors based on aminoquinazoline cores. Compounds 72–77 demonstrated varied whole cell activity against Gram‐positive bacteria (MIC = 0.51–264 μM), while compounds 78–81 possessed micromolar potency (IC 50 = 1.3–74 μM) 79,104–106 . These series of inhibitors are predicted to bind within the hydrophobic pocket, occupying part of the UTP‐binding site and locking GlmU in an apo‐enzyme‐like conformation 79,104–106 .…”

Endless resistance. Endless antibiotics?

“…106 A recent example of successful virtual screening include the identification of inhibitors of the Penicillin-Binding Proteins having promising in vitro Gram-positive activity. [107][108][109] Other examples include efforts directed toward the cytoskeletal protein FtsZ; 110,111 the sortase transpeptidases; 112,113 the GlmU uridyltransferase (from a lead identified by high-through put screening); 114,115 and the Mur enzymes of peptidoglycan biosynthesis. [116][117][118] The qualification of "promising" for all of these structures (again) refers to the momentous difficulty of taking a structure from in vitro activity to clinical efficacy.…”