9q46

Ternary complex of PYCR1 with the allosteric inhibitor 2-[(2,6-dichlorophenyl)amino]pyridine-3-sulfonic acid in two remote sites and the active site, and (S)-(-)-2-Hydroxy-3,3-dimethylbutyric acid in the active site

spinqualitylabelsall models 9q46, resolution 1.75Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 9q46 is a 5 chain structure with sequence from Homo sapiens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.75Å Ligands: A1CFJ, G8I, SO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed Delta1-pyrroline-5-carboxylate (P5C) reductase 1 (PYCR1) catalyzes the NAD(P)H-dependent conversion of L-P5C to L-proline and is one of the most consistently upregulated metabolic enzymes in cancer cells. High PYCR1 expression is associated with adverse clinical outcomes, and its knockdown inhibits tumor proliferation and metastasis, motivating inhibitor discovery. All structurally validated PYCR1 inhibitors to date bind in the active site and are anchored in the L-P5C binding pocket by an anionic functional group, typically carboxylate. Seeking inhibitors with alternative anchors, we used X-ray crystallography to screen 22 fragment-like compounds (MW = 189-343 Da) from docking that represent six different carboxylic acid isosteres. Surprisingly, only one compound bound in the active site. Four other compounds were found in three adjacent remote sites located in oligomer interfaces. The compounds bind 7 A from NADH and 10-14 A from L-P5C, and the intervening space is blocked by protein for inhibitors in Sites 1A/1B and open for inhibitors in Site 2. Together, the three binding sites define a ligand binding hot spot groove that spans 33 A. The remote binders inhibit PYCR1 activity with K values from the mixed model of inhibition of 32 muM to 2 mM. Co-crystal structures of PYCR1 with combinations of allosteric inhibitors, NADH, and L-P5C/proline analogs suggest the inhibitors can bind to the ternary PYCR1-L-P5C-NAD(P)H complex in addition to the free enzyme, consistent with a mixed mechanism of inhibition. The discovery of an allosteric inhibitor binding groove that accommodates multiple fragments heralds a new era of PYCR1 inhibitor design. Serendipitous Discovery of an Allosteric Inhibitor Binding Groove in the Proline Biosynthetic Enzyme Pyrroline-5-Carboxylate Reductase 1 (PYCR1).,Meeks KR, Mattingly CJ, Nix JC, Chuk O, Protopopov MV, Tarkhanova OO, Tanner JJ Biochem J. 2026 Jan 22:BCJ20250278. doi: 10.1042/BCJ20250278. PMID:41569420 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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