2wuw

Crystallographic analysis of counter-ion effects on subtilisin enzymatic action in acetonitrile (native data)

spinqualitylabelsall models 2wuw, resolution 2.23Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2wuw is a 1 chain structure with sequence from Bacillus licheniformis. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CA, CCN, NA, SO4 Related: 1sel, 1yu6, 1avt, 1r0r, 1av7, 2sec, 1scn, 1oyv, 1c3l, 1vsb, 3vsb, 2wuv Activity: Subtilisin, with EC number 3.4.21.62 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [SUBT_BACLI] Subtilisin is an extracellular alkaline serine protease, it catalyzes the hydrolysis of proteins and peptide amides. Publication Abstract from PubMed When enzymes are in low dielectric nonaqueous media, it would be expected that their charged groups would be more closely associated with counterions. There is evidence that these counterions may then affect enzymatic activity. Published crystal structures of proteins in organic solvents do not show increased numbers of associated counterions, and this might reflect the difficulty of distinguishing cations like Na(+) from water molecules. In this paper, the placement of several Cs(+) and Cl(-) ions in crystals of the serine protease subtilisin Carlsberg is presented. Ions are more readily identified crystallographically through their anomalous diffraction using softer X-rays. The protein conformation is very similar to that of the enzyme without CsCl in acetonitrile, both for the previously reported ( 1SCB ) and our own newly determined model. No fewer than 11 defined sites for Cs(+) cations and 8 Cl(-) anions are identified around the protein molecule, although most of these have partial occupancy and may represent nonspecific binding sites. Two Cs(+) and two Cl(-) ions are close to the mouth of the active site cleft, where they may affect catalysis. In fact, cross-linked CsCl-treated subtilisin crystals transferred to acetonitrile show catalytic activity several fold higher than the reference crystals containing Na(+). Presoaking with another large cation, choline, also increases the enzyme activity. The active site appears only minimally sterically perturbed by the ion presence around it, so alternative activation mechanisms can be suggested: an electrostatic redistribution and/or a larger hydration sphere that enhances the protein domain. Crystallographic analysis of counterion effects on subtilisin enzymatic action in acetonitrile.,Cianci M, Tomaszewski B, Helliwell JR, Halling PJ J Am Chem Soc. 2010 Feb 24;132(7):2293-300. PMID:20099851 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Subtilisin

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