1gbt: Difference between revisions

Revision as of 17:23, 2 May 2008

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

OverviewOverview

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)

About this StructureAbout this Structure

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

ReferenceReference

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 Page seeded by OCA on Fri May 2 17:23:20 2008

Proteopedia Page Contributors and Editors (what is this?)Proteopedia Page Contributors and Editors (what is this?)

OCA

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 [[Image:1gbt.jpg|left|200px]]
- {{Structure
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+The line below this paragraph, containing "STRUCTURE_1gbt", creates the "Structure Box" on the page.
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-|LIGAND= <scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=GBS:4-GUANIDINOBENZOIC+ACID'>GBS</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</scene>
+or the SCENE parameter (which sets the initial scene displayed when the page is loaded),
-|ACTIVITY= <span class='plainlinks'>[http://en.wikipedia.org/wiki/Trypsin Trypsin], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.21.4 3.4.21.4] </span>
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-|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1gbt FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1gbt OCA], [http://www.ebi.ac.uk/pdbsum/1gbt PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1gbt RCSB]</span>
-}}
 '''STRUCTURE OF AN ACYL-ENZYME INTERMEDIATE DURING CATALYSIS: (GUANIDINOBENZOYL) TRYPSIN'''
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 [[Category: Singer, P T.]]
 [[Category: Sweet, R M.]]
-[[Category: hydrolase(serine proteinase)]]
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May  2 17:23:20 2008''
-''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Mar 30 20:40:54 2008''