Fig. 1 BRD1389 binds cFRS selectively and inhibits aminoacylation via L-Phe competition. a Chemical structure of BRD1389. b Inhibition of the aminoacylation activity of Pf (Plasmodium falciparum) , Pv (Plasmodium vivax) , Hs ( Homo sapiens ) and Pf mutant (L550V) cFRS enzymes by BRD1389. These assays were performed at concentrations ranging from 100 μ M to 0.1 nM and the IC 50 values were calculated by non-linear regression. Data are shown as mean ± SD ( n = 3 independent experiments). c , d Mode of BRD1389 inhibition. BRD1389 is a competitive inhibitor of Pf cFRS with respect to L-Phe ( K i = 6 nM) while it is likely a non-competitive inhibitor with respect to ATP ( K i = 10 nM). Lineweaver-Burk plots were obtained at a saturating concentration of either ATP (500 μ M) or L-Phe (1000 μ M) with varying concentrations of other substrate: L-Phe (1000 – 15.6 μ M) or ATP (500 – 15.6 μ M) and inhibitor BRD1389 (1 × IC 50 (blue triangle), 0.5 × IC 50 (yellow square), and 0 × IC 50 (black circle) Data are shown as mean ± SD ( n = 3 independent experiments). The error bars indicate standard deviation ( n = 3). e , f Surface view of heterodimeric assembly ( αβ ) of Pv cFRS and Hs cFRS ( α -subunit in grey and β -subunit in pink) structures. The subdomains of β 1 and β 2 of β -subunit are marked. g Superimposed structure of Pv/Hs cFRS displaying movement of subdomain β 2 of β -subunit and hence the possible domain swap in the malaria enzyme. h Close-up view of β -subunit linker region indicating the three residue insertion (red) in Hs cFRS, which when absent may lead to domain swap. i , j Surface view of the heterotetrametric assembly ( αβ ) 2 of both Pv and Hs cFRS structures ( α -subunit is in grey and β -subunit is in plum whereas the symmetry related α ′ and β ′ domains are shown in light green and orange respectively). k Portion of the sequence alignment showing the linker region between β 1 and β 2 subdomains of the β -subunit in Pv cFRS versus Hs cFRS. Source data are provided as a Source Data fi le.