3t8u

Crystal structure of ketosteroid isomerase Y14AY55FD99A from Pseudomonas testosteroni

spinqualitylabelsall models 3t8u, resolution 2.50Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3t8u is a 4 chain structure with sequence from Atcc 11996. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: SO4 Related: 3rgr, 3t8n, 3m8c Gene: ksi (ATCC 11996) Activity: Steroid Delta-isomerase, with EC number 5.3.3.1 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed Prior site-directed mutagenesis studies in bacterial ketosteroid isomerase (KSI) reported that substitution of both oxyanion hole hydrogen bond donors give a 10^5-10^8 fold rate reduction suggesting that the oxyanion hole may provide the major contribution to KSI catalysis. But these seemingly conservative mutations replaced the oxyanion hole hydrogen bond donors with hydrophobic side chains that could lead to suboptimal solvation of the incipient oxyanion in the mutants, thereby potentially exaggerating the apparent energetic benefit of the hydrogen bonds relative to water-mediated hydrogen bonds in solution. We determined the functional and structural consequences of substituting the oxyanion hole hydrogen bond donors and several residues surrounding the oxyanion hole with smaller residues in an attempt to create a local site that would provide interactions more analogous to those in aqueous solution. These more drastic mutations created an active site cavity estimated to be ~650 A^3 and sufficient for occupancy by 15-17 water molecules and led to a rate decrease of only ~10^3-fold for KSI from two different species, a much smaller effect than that observed from more traditional conservative mutations. The results underscore the strong context dependence of hydrogen bond energetics and suggest that the oxyanion hole provides an important, but moderate, catalytic contribution relative to the interactions in the corresponding solution reaction. Evaluating the Catalytic Contribution from the Oxyanion Hole in Ketosteroid Isomerase.,Schwans JP, Sunden F, Gonzalez A, Tsai Y, Herschlag D J Am Chem Soc. 2011 Nov 4. PMID:22053826 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Ketosteroid Isomerase

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