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1ab9

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{{STRUCTURE_1ab9| PDB=1ab9 | SCENE= }}
{{STRUCTURE_1ab9| PDB=1ab9 | SCENE= }}
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'''CRYSTAL STRUCTURE OF BOVINE GAMMA-CHYMOTRYPSIN'''
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===CRYSTAL STRUCTURE OF BOVINE GAMMA-CHYMOTRYPSIN===
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==Overview==
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The dipeptide D-leucyl-L-phenylalanyl p-fluorobenzylamide (D-Leu-Phe-NH-BzlF) inhibits chymotrypsin strongly in a competitive manner with the Ki value of 0.61 microM [Shimohigashi, Y., Maeda, I., Nose, T., Ikesue, K., Sakamoto, H., Ogawa, T., Ide, Y., Kawahara, M., Nezu, T., Terada, Y., Kawano, K. &amp; Ohno, M. (1996) J. Chem. Soc. Perkin Trans. 1, 2479-2485]. The structure/activity studies have suggested a unique inhibitory conformation, in which the C-terminal benzyl group fits the chymotrypsin S1 site and the hydrophobic core constructed by the side chains of D-Leu-Phe fits the S2 or S1' site. To verify this assumption, the molecular structure of the complex between the dipeptide and gamma-chymotrypsin has been determined crystallographically. Gamma-chymotrypsin itself was first crystallized and refined at 1.6-A resolution. The refined structure was virtually identical to the conformation reported and the electron density at the active site was interpreted as a pentapeptide Thr-Pro-Gly-Val-Tyr derived from autolysis of the enzyme (residues 224-228). The chymotrypsin-dipeptide complex was obtained by soaking the crystals of gamma-chymotrypsin in a solution saturated with the dipeptide inhibitor. The crystal structure of the complex has been refined at 1.8-A resolution to a crystallographic R-factor of 18.1%. The structure of gamma-chymotrypsin in the complex agreed fairly well with that of gamma-chymotrypsin per se with a rmsd of 0.13 A for all the C alpha carbons. Two inhibitor molecules were assigned in an asymmetric unit, i.e. one in the active site and the other at the interface of two symmetry-related enzyme molecules. In both sites dipeptides adopted very similar folded conformations, in which side chains of D-Leu-Phe are spatially proximal. In the active site where the binding of dipeptide was judged to be a direct cause of inhibition, C-terminal p-fluorobenzylamide group of the dipeptide, NH-BzlF, was found in the S1 hydrophobic pocket. At the bottom of this pocket, the p-fluorine atom hydrogen bonded with a water molecule, probably to enhance the inhibitory activity. The stereospecific interaction of R and S isomers of the dipeptide with C-terminal NH-C*H(CH3)-C6H5 was well explained by the space available for methyl replacement in the complex. The hydrophobic core constructed by side chains of D-Leu-Phe was found at the broad S2 site. Interestingly, a novel interaction was found between the inhibitor Phe residue and chymotrypsin His57, the phenyl of Phe and the imidazole of His being in a pi-pi stacking interaction at a distance 3.75 A.
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(as it appears on PubMed at http://www.pubmed.gov), where 9692896 is the PubMed ID number.
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{{ABSTRACT_PUBMED_9692896}}
==About this Structure==
==About this Structure==
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[[Category: Serine protease]]
[[Category: Serine protease]]
[[Category: Zymogen]]
[[Category: Zymogen]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 10:04:15 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 16:31:35 2008''

Revision as of 13:31, 30 June 2008

Image:1ab9.png

Template:STRUCTURE 1ab9

CRYSTAL STRUCTURE OF BOVINE GAMMA-CHYMOTRYPSIN

Template:ABSTRACT PUBMED 9692896

About this Structure

1AB9 is a Protein complex structure of sequences from Bos taurus. Full crystallographic information is available from OCA.

Reference

X-ray crystal structure of a dipeptide-chymotrypsin complex in an inhibitory interaction., Kashima A, Inoue Y, Sugio S, Maeda I, Nose T, Shimohigashi Y, Eur J Biochem. 1998 Jul 1;255(1):12-23. PMID:9692896

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