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PDBsum entry 1be8
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Serine protease
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PDB id
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1be8
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References listed in PDB file
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Key reference
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Title
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Comparison of X-Ray crystal structures of an acyl-Enzyme intermediate of subtilisin carlsberg formed in anhydrous acetonitrile and in water.
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Authors
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J.L.Schmitke,
L.J.Stern,
A.M.Klibanov.
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Ref.
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Proc Natl Acad Sci U S A, 1998,
95,
12918-12923.
[DOI no: ]
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PubMed id
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Abstract
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The x-ray crystal structures of trans-cinnamoyl-subtilisin, an acyl-enzyme
covalent intermediate of the serine protease subtilisin Carlsberg, have been
determined to 2.2-A resolution in anhydrous acetonitrile and in water. The
cinnamoyl-subtilisin structures are virtually identical in the two solvents. In
addition, their enzyme portions are nearly indistinguishable from previously
determined structures of the free enzyme in acetonitrile and in water; thus,
acylation in either aqueous or nonaqueous solvent causes no appreciable
conformational changes. However, the locations of bound solvent molecules in the
active site of the acyl- and free enzyme forms in acetonitrile and in water are
distinct. Such differences in the active site solvation may contribute to the
observed variations in enzymatic activities. On prolonged exposure to organic
solvent or removal of interstitial solvent from the crystal lattice, the
channels within enzyme crystals are shown to collapse, leading to a drop in the
number of active sites accessible to the substrate. The mechanistic and
preparative implications of our findings for enzymatic catalysis in organic
solvents are discussed.
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Figure 1.
Fig. 1. Ribbon diagram of the protein structure of
trans-cinnamoyl-subtilisin in acetonitrile. The catalytic triad
(Asp-32, His-64, and Ser-221) is portrayed as sticks. The
cinnamoyl group is shown in black. Water molecules and
acetonitrile molecules are depicted by balls-and-sticks, with
the nitrogen atoms of acetonitrile in black.
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Figure 2.
Fig. 2. Ribbon diagram of the protein structure of
trans-cinnamoyl-subtilisin in water. The catalytic triad and
cinnamoyl group (black) are portrayed as sticks. Water molecules
are depicted by gray balls.
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