4hhq

Serum paraoxonase-1 by directed evolution with the H115Q and H134Q mutations

spinqualitylabelsall models 4hhq, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4hhq is a 1 chain structure with sequence from Synthetic construct. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.3Å Ligands: BR, CA, LMT Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed Although largely deemed as structurally conserved, catalytic metal ion sites can rearrange, thereby contributing to enzyme evolvability. Here, we show that in paraoxonase-1, a lipo-lactonase, catalytic promiscuity and divergence into an organophosphate hydrolase are correlated with an alternative mode of the catalytic Ca. We describe the crystal structures of active-site mutants bearing mutations at position 115. The histidine at this position acts as a base to activate the lactone-hydrolyzing water molecule. Mutations to Trp or Gln indeed diminish paraoxonase-1's lactonase activity; however, the promiscuous organophosphate hydrolase activity is enhanced. The structures reveal a 1.8-A upward displacement towards the enzyme's surface of the catalytic Ca in the His115 mutants and configurational changes in the ligating side chains and water molecules, relative to the wild-type enzyme. Biochemical analysis and molecular dynamics simulations suggest that this alternative, upward metal mode mediates the promiscuous hydrolysis of organophosphates. The upward Ca mode observed in the His115 mutants also appears to mediate the wild type's paraoxonase activity. However, whereas the upward mode dominates in the Trp115 mutant, it is scarcely populated in wild type. Thus, the plasticity of active-site metal ions may permit alternative, latent, promiscuous activities and also provide the basis for the divergence of new enzymatic functions. Catalytic metal ion rearrangements underline promiscuity and evolvability of a metalloenzyme.,Ben-David M, Wieczorek G, Elias M, Silman I, Sussman JL, Tawfik DS J Mol Biol. 2013 Mar 25;425(6):1028-38. doi: 10.1016/j.jmb.2013.01.009. Epub 2013, Jan 11. PMID:23318950 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Serum Paraoxonase

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