6b8r | pdb_00006b8r

Crystal structure of Staphylococcal nuclease variant Delta+PHS V23K/L36Q at cryogenic temperature

spinqualitylabelsall models 6b8r, resolution 1.65Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6b8r is a 1 chain structure with sequence from Staphylococcus aureus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.65Å Ligands: CA, THP Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function NUC_STAAU Enzyme that catalyzes the hydrolysis of both DNA and RNA at the 5' position of the phosphodiester bond. Publication Abstract from PubMed Thirty years ago, Hwang and Warshel suggested that a microenvironment preorganized to stabilize an ion pair would be incapable of reorganizing to stabilize the reverse ion pair. The implications were that (1) proteins have a limited capacity to reorganize, even under the influence of strong interactions, such as those present when ionizable groups are buried in the hydrophobic interior of a protein, and (2) the inability of proteins to tolerate the reversal of buried ion pairs demonstrates the limitations inherent to continuum electrostatic models of proteins. Previously we showed that when buried individually in the interior of staphylococcal nuclease, Glu23 and Lys36 have p Ka values near pH 7, but when buried simultaneously, they establish a strong interaction of approximately 5 kcal/mol and have p Ka values shifted toward more normal values. Here, using equilibrium thermodynamic measurements, crystal structures, and NMR spectroscopy experiments, we show that although the reversed, individual substitutions-Lys23 and Glu36-also have p Ka values near 7, when buried together, they neither establish a strong interaction nor promote reorganization of their microenvironment. These experiments both confirm Warshel's original hypothesis and expand it by showing that it applies to reorganization, as demonstrated by our artificial ion pairs, as well as to preorganization as is commonly argued for motifs that stabilize naturally occurring ion pairs in polar microenvironments. These data constitute a challenging benchmark useful to test the ability of structure-based algorithms to reproduce the compensation between self-energy, Coulomb and polar interactions in hydrophobic environments of proteins. Dielectric Properties of a Protein Probed by Reversal of a Buried Ion Pair.,Robinson AC, Schlessman JL, Garcia-Moreno E B J Phys Chem B. 2018 Mar 8;122(9):2516-2524. doi: 10.1021/acs.jpcb.7b12121. Epub, 2018 Feb 21. PMID:29466010 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Staphylococcal nuclease 3D structures

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