1c7t
From Proteopedia
(New page: 200px<br /><applet load="1c7t" size="450" color="white" frame="true" align="right" spinBox="true" caption="1c7t, resolution 1.90Å" /> '''BETA-N-ACETYLHEXOSAM...) |
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| - | [[Image:1c7t.gif|left|200px]]<br /><applet load="1c7t" size=" | + | [[Image:1c7t.gif|left|200px]]<br /><applet load="1c7t" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1c7t, resolution 1.90Å" /> | caption="1c7t, resolution 1.90Å" /> | ||
'''BETA-N-ACETYLHEXOSAMINIDASE MUTANT E540D COMPLEXED WITH DI-N ACETYL-D-GLUCOSAMINE (CHITOBIASE)'''<br /> | '''BETA-N-ACETYLHEXOSAMINIDASE MUTANT E540D COMPLEXED WITH DI-N ACETYL-D-GLUCOSAMINE (CHITOBIASE)'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The catalytic domain of chitobiase (beta-N-1-4 acetylhexosaminidase) from | + | The catalytic domain of chitobiase (beta-N-1-4 acetylhexosaminidase) from Serratia marcescens, is an alpha/beta TIM-barrel. This enzyme belongs to family 20 of glycosyl hydrolases in which a conserved amino acid pair, aspartate-glutamate, is present (Asp539-Glu540). It was proposed that catalysis by this enzyme family is carried out by glutamate 540 acting as a proton donor and by the acetamido group of the substrate as a nucleophile. We investigated the role of Asp539 and Glu540 by site-directed mutagenesis, biochemical characterization and by structural analyses of chitobiase -substrate co-crystals. We found that both residues are essential for chitobiase activity. The mutations, however, led to subtle changes in the catalytic site. Our results support the model that Glu540 acts as the proton donor and that Asp539 acts in several different ways. Asp539 restrains the acetamido group of the substrate in a specific orientation by forming a hydrogen bond with N2 of the non-reduced (-1) sugar. In addition, this residue participates in substrate binding. It is also required for the correct positioning of Glu540 and may provide additional negative charge at the active site. Thus, these biochemical and structural studies provide a molecular explanation for the functional importance and conservation of these residues. |
==About this Structure== | ==About this Structure== | ||
| - | 1C7T is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Serratia_marcescens Serratia marcescens] with CBS and SO4 as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Beta-N-acetylhexosaminidase Beta-N-acetylhexosaminidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.52 3.2.1.52] Full crystallographic information is available from [http:// | + | 1C7T is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Serratia_marcescens Serratia marcescens] with <scene name='pdbligand=CBS:'>CBS</scene> and <scene name='pdbligand=SO4:'>SO4</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Beta-N-acetylhexosaminidase Beta-N-acetylhexosaminidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.52 3.2.1.52] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1C7T OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Serratia marcescens]] | [[Category: Serratia marcescens]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Oppenheim, A | + | [[Category: Oppenheim, A B.]] |
[[Category: Papanikolau, Y.]] | [[Category: Papanikolau, Y.]] | ||
[[Category: Petratos, K.]] | [[Category: Petratos, K.]] | ||
[[Category: Prag, G.]] | [[Category: Prag, G.]] | ||
[[Category: Tavlas, G.]] | [[Category: Tavlas, G.]] | ||
| - | [[Category: Vorgias, C | + | [[Category: Vorgias, C E.]] |
[[Category: CBS]] | [[Category: CBS]] | ||
[[Category: SO4]] | [[Category: SO4]] | ||
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[[Category: x-ray diffraction]] | [[Category: x-ray diffraction]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:03:17 2008'' |
Revision as of 10:03, 21 February 2008
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BETA-N-ACETYLHEXOSAMINIDASE MUTANT E540D COMPLEXED WITH DI-N ACETYL-D-GLUCOSAMINE (CHITOBIASE)
Overview
The catalytic domain of chitobiase (beta-N-1-4 acetylhexosaminidase) from Serratia marcescens, is an alpha/beta TIM-barrel. This enzyme belongs to family 20 of glycosyl hydrolases in which a conserved amino acid pair, aspartate-glutamate, is present (Asp539-Glu540). It was proposed that catalysis by this enzyme family is carried out by glutamate 540 acting as a proton donor and by the acetamido group of the substrate as a nucleophile. We investigated the role of Asp539 and Glu540 by site-directed mutagenesis, biochemical characterization and by structural analyses of chitobiase -substrate co-crystals. We found that both residues are essential for chitobiase activity. The mutations, however, led to subtle changes in the catalytic site. Our results support the model that Glu540 acts as the proton donor and that Asp539 acts in several different ways. Asp539 restrains the acetamido group of the substrate in a specific orientation by forming a hydrogen bond with N2 of the non-reduced (-1) sugar. In addition, this residue participates in substrate binding. It is also required for the correct positioning of Glu540 and may provide additional negative charge at the active site. Thus, these biochemical and structural studies provide a molecular explanation for the functional importance and conservation of these residues.
About this Structure
1C7T is a Single protein structure of sequence from Serratia marcescens with and as ligands. Active as Beta-N-acetylhexosaminidase, with EC number 3.2.1.52 Full crystallographic information is available from OCA.
Reference
Structures of chitobiase mutants complexed with the substrate Di-N-acetyl-d-glucosamine: the catalytic role of the conserved acidic pair, aspartate 539 and glutamate 540., Prag G, Papanikolau Y, Tavlas G, Vorgias CE, Petratos K, Oppenheim AB, J Mol Biol. 2000 Jul 14;300(3):611-7. PMID:10884356
Page seeded by OCA on Thu Feb 21 12:03:17 2008
Categories: Beta-N-acetylhexosaminidase | Serratia marcescens | Single protein | Oppenheim, A B. | Papanikolau, Y. | Petratos, K. | Prag, G. | Tavlas, G. | Vorgias, C E. | CBS | SO4 | A/b(tim)-barrel | Beta-n-acetylhexosaminidase | Chitinolysin | Co-crystal structure | Glycosyl hydrolase | Proton donor | Site directed mutagenesis | X-ray diffraction
