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| [[Image:2nt9.jpg|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_2nt9| PDB=2nt9 | SCENE= }} | | {{STRUCTURE_2nt9| PDB=2nt9 | SCENE= }} |
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| '''Crystal structure of pectin methylesterase D178A mutant in complex with hexasaccharide IV'''
| | ===Crystal structure of pectin methylesterase D178A mutant in complex with hexasaccharide IV=== |
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| ==Overview==
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| We provide a mechanism for the activity of pectin methylesterase (PME), the enzyme that catalyses the essential first step in bacterial invasion of plant tissues. The complexes formed in the crystal using specifically methylated pectins, together with kinetic measurements of directed mutants, provide clear insights at atomic resolution into the specificity and the processive action of the Erwinia chrysanthemi enzyme. Product complexes provide additional snapshots along the reaction coordinate. We previously revealed that PME is a novel aspartic-esterase possessing parallel beta-helix architecture and now show that the two conserved aspartates are the nucleophile and general acid-base in the mechanism, respectively. Other conserved residues at the catalytic centre are shown to be essential for substrate binding or transition state stabilisation. The preferential binding of methylated sugar residues upstream of the catalytic site, and demethylated residues downstream, drives the enzyme along the pectin molecule and accounts for the sequential pattern of demethylation produced by both bacterial and plant PMEs.
| | The line below this paragraph, {{ABSTRACT_PUBMED_17717531}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 17717531 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_17717531}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Hydrolase]] | | [[Category: Hydrolase]] |
| [[Category: Michaelis complex]] | | [[Category: Michaelis complex]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 09:53:08 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 06:19:16 2008'' |