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1gbt

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{{STRUCTURE_1gbt| PDB=1gbt | SCENE= }}
{{STRUCTURE_1gbt| PDB=1gbt | SCENE= }}
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'''STRUCTURE OF AN ACYL-ENZYME INTERMEDIATE DURING CATALYSIS: (GUANIDINOBENZOYL) TRYPSIN'''
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===STRUCTURE OF AN ACYL-ENZYME INTERMEDIATE DURING CATALYSIS: (GUANIDINOBENZOYL) TRYPSIN===
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==Overview==
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The crystal and molecular structure of trypsin at a transiently stable intermediate step during catalysis has been determined by X-ray diffraction methods. Bovine trypsin cleaved the substrate p-nitrophenyl p-guanidinobenzoate during crystallization under conditions in which the acyl-enzyme intermediate, (guanidinobenzoyl)trypsin, was stable. Orthorhombic crystals formed in space group P2(1)2(1)2(1), with a = 63.74, b = 63.54, and c = 68.93 A. This is a crystal form of bovine trypsin for which a molecular structure has not been reported. Diffraction data were measured with a FAST (Enraf Nonius) diffractometer. The structure was refined to a crystallographic residual of R = 0.16 for data in the resolution range 7.0-2.0 A. The refined model of (guanidinobenzoyl)trypsin provides insight into the structural basis for its slow rate of deacylation, which in solution at 25 degrees C and pH 7.4 exhibits a t1/2 of 12 h. In addition to the rotation of the Ser-195 hydroxyl away from His-157, C beta of Ser-195 moves 0.7 A toward Asp-189 at the bottom of the active site, with respect to the native structure. This allows formation of energetically favorable H bonds and an ion pair between the carboxylate of Asp-189 and the guanidino group of the substrate. This movement is dictated by the rigidity of the aromatic ring in guanidinobenzoate--model-building indicates that this should not occur when arginine, with its more flexible aliphatic backbone, forms the ester bond with Ser-195. As a consequence, highly ordered water molecules in the active site are no longer close enough to the scissile ester bond to serve as potential nucleophiles for hydrolysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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{{ABSTRACT_PUBMED_2252895}}
==About this Structure==
==About this Structure==
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[[Category: Singer, P T.]]
[[Category: Singer, P T.]]
[[Category: Sweet, R M.]]
[[Category: Sweet, R M.]]
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Revision as of 02:02, 1 July 2008

Image:1gbt.png

Template:STRUCTURE 1gbt

STRUCTURE OF AN ACYL-ENZYME INTERMEDIATE DURING CATALYSIS: (GUANIDINOBENZOYL) TRYPSIN

Template:ABSTRACT PUBMED 2252895

About this Structure

1GBT is a Single protein structure of sequence from Bos taurus. Full crystallographic information is available from OCA.

Reference

Structure of an acyl-enzyme intermediate during catalysis: (guanidinobenzoyl)trypsin., Mangel WF, Singer PT, Cyr DM, Umland TC, Toledo DL, Stroud RM, Pflugrath JW, Sweet RM, Biochemistry. 1990 Sep 11;29(36):8351-7. PMID:2252895

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