Fig. 7: The mechanism of inhibition and selectivity of Compound ATB3 toward hUTA2. | Nature Communications

Fig. 7: The mechanism of inhibition and selectivity of Compound ATB3 toward hUTA2.

From: Structural insights into the mechanisms of urea permeation and distinct inhibition modes of urea transporters

Fig. 7

a The concentration dependent blockade of urea transport of hUT-A2 by compound ATB3. Data are shown as mean ± SEM of three independent experiments (n = 3). b The extracellular blocker binding pocket (EBBP) and cytoplasmic blocker binding pocket (CBBP) of ATB3 in hUT-A2. c, d The interactions between hUT-A2 and ATB3 in EBBP (c) or CBBP) (d). The H-bonds are shown as red dashed lines. e Structural comparison of 25a and ATB3 in EBBP. f The ATB3 occupied three subpockets in the extracellular side, the EBBP1, EBBP2, and EUBP. Residues forming polar interactions or hydrogen bonds with ATB3 are depicted using triangles. Residues forming hydrophobic or van der Waals interactions are depicted as solid round circles. The residues F135, L202, and L284 are shared by both EBBP1 and EBBP2. g, h. The methoxy groups of ATB3 formed hydrophobic interaction with L202 and P336 in hUT-A2, whereas ATB3 don’t form similar interactions with structural equivalent amino acid V203 and A337 in hUT-B. The black dashed lines represent the shortest distance. i Barcode comparisons of the residues involving in the EBBP of different UTs. The residues engaged interactions with 25a, ATB3 and HQA2 are colored orange, and the special residues only interact with ATB3 or HQA2 are colored red or green, respectively. The amino acid of hUT-A2 are displayed on the top line and bottom, with the residues in “L-P” pocket and “SCG” pocket colored magenta and green, respectively. The letters inside the black circles represent the non-conserved amino acids of hUT-A3 or hUT-B. j The comparison between the best estimate residue energy contributions of residues L202 or P336 for their interaction with ATB3 and their corresponding L202V, P336A mutants. k Effects of hUT-A2 mutants L202V and P336A on the ATB3 activity toward hUT-A2. Values are mean ± SEM from three independent experiments (n = 3). l The diagram of ATB3 engaging with the urea binding pocket or “L-P” pocket with the interfaces represented by blue or violet dashed lines, respectively.

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