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| [[Image:1epo.jpg|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_1epo| PDB=1epo | SCENE= }} | | {{STRUCTURE_1epo| PDB=1epo | SCENE= }} |
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| '''DIRECT OBSERVATION BY X-RAY ANALYSIS OF THE TETRAHEDRAL "INTERMEDIATE" OF ASPARTIC PROTEINASES'''
| | ===DIRECT OBSERVATION BY X-RAY ANALYSIS OF THE TETRAHEDRAL "INTERMEDIATE" OF ASPARTIC PROTEINASES=== |
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| ==Overview==
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| We report the X-ray analysis at 2.0 A resolution for crystals of the aspartic proteinase endothiapepsin (EC 3.4.23.6) complexed with a potent difluorostatone-containing tripeptide renin inhibitor (CP-81,282). The scissile bond surrogate, an electrophilic ketone, is hydrated in the complex. The pro-(R) (statine-like) hydroxyl of the tetrahedral carbonyl hydrate is hydrogen-bonded to both active-site aspartates 32 and 215 in the position occupied by a water in the native enzyme. The second hydroxyl oxygen of the hydrate is hydrogen-bonded only to the outer oxygen of Asp 32. These experimental data provide a basis for a model of the tetrahedral intermediate in aspartic proteinase-mediated cleavage of the amide bond. This indicates a mechanism in which Asp 32 is the proton donor and Asp 215 carboxylate polarizes a bound water for nucleophilic attack. The mechanism involves a carboxylate (Asp 32) that is stabilized by extensive hydrogen bonding, rather than an oxyanion derivative of the peptide as in serine proteinase catalysis.
| | The line below this paragraph, {{ABSTRACT_PUBMED_1304340}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 1304340 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_1304340}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Cooper, J B.]] | | [[Category: Cooper, J B.]] |
| [[Category: Veerapandian, B.]] | | [[Category: Veerapandian, B.]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 15:22:56 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 01:32:30 2008'' |
