The identification of inhibitory compounds of Rickettsia prowazekii methionine aminopeptidase for antibacterial applications

Abstract

Methionine aminopeptidase (MetAP) is a dinuclear metalloprotease responsible for the cleavage of methionine initiator residues from nascent proteins. MetAP activity is necessary for bacterial proliferation and is therefore a projected novel antibacterial target. A compound library consisting of 294 members containing metal-binding functional groups was screened against Rickettsia prowazekii MetAP to determine potential inhibitory motifs. The compounds were first screened against the target at a concentration of 10 µM and potential hits were determined to be those exhibiting greater than 50% inhibition of enzymatic activity. These hit compounds were then rescreened against the target in 8-point dose-response curves and 11 compounds were found to inhibit enzymatic activity with IC₅₀ values of less than 10 µM. Finally, compounds (1-5) were docked against RpMetAP with AutoDock to determine potential binding mechanisms and the results were compared with crystal structures deposited within the PDB.

Figure 1

Left: RpMetAP with active site residues displayed; Mn(II) cofactors are shown as purple spheres. Right: Zoom-in of the RpMetAP active site with bound Mn(II) cofactors (PDB 3MX6).

Figure 2

Comparison of the known binding mechanism of furoic acid-based inhibitors against EcMetAP (left, PDB: 1XNZ) and the predicted docking pose of sulfonamide (1) against RpMetAP (right). Compound (1) was predicted to bind via chelation to the Mn(II) cofactors through the acid functionality which mirrors the experimentally determined binding mechanism depicted for EcMetAP containing 5-(2-chlorophenyl)-2-furoic acid.

Scheme 1