View source for 1gbt

[[Image:1gbt.jpg|left|200px]]

 {{Structure
|PDB= 1gbt |SIZE=350|CAPTION= <scene name='initialview01'>1gbt</scene>, resolution 2.0&Aring;
|SITE= 
|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>
|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>
|GENE= 
|DOMAIN=
|RELATEDENTRY=
|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'''


==Overview==
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 Structure==
1GBT is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Bos_taurus Bos taurus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1GBT 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:[http://www.ncbi.nlm.nih.gov/pubmed/2252895 2252895]
[[Category: Bos taurus]]
[[Category: Single protein]]
[[Category: Trypsin]]
[[Category: Singer, P T.]]
[[Category: Sweet, R M.]]
[[Category: hydrolase(serine proteinase)]]

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