1m01
From Proteopedia
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| - | [[Image:1m01.gif|left|200px]] | + | [[Image:1m01.gif|left|200px]] |
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| - | '''Wildtype Streptomyces plicatus beta-hexosaminidase in complex with product (GlcNAc)''' | + | {{Structure |
| + | |PDB= 1m01 |SIZE=350|CAPTION= <scene name='initialview01'>1m01</scene>, resolution 2.10Å | ||
| + | |SITE= | ||
| + | |LIGAND= <scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene>, <scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</scene> and <scene name='pdbligand=GOL:GLYCEROL'>GOL</scene> | ||
| + | |ACTIVITY= [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] | ||
| + | |GENE= | ||
| + | }} | ||
| + | |||
| + | '''Wildtype Streptomyces plicatus beta-hexosaminidase in complex with product (GlcNAc)''' | ||
| + | |||
==Overview== | ==Overview== | ||
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==About this Structure== | ==About this Structure== | ||
| - | 1M01 is a [ | + | 1M01 is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Streptomyces_plicatus Streptomyces plicatus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1M01 OCA]. |
==Reference== | ==Reference== | ||
| - | Aspartate 313 in the Streptomyces plicatus hexosaminidase plays a critical role in substrate-assisted catalysis by orienting the 2-acetamido group and stabilizing the transition state., Williams SJ, Mark BL, Vocadlo DJ, James MN, Withers SG, J Biol Chem. 2002 Oct 18;277(42):40055-65. Epub 2002 Aug 8. PMID:[http:// | + | Aspartate 313 in the Streptomyces plicatus hexosaminidase plays a critical role in substrate-assisted catalysis by orienting the 2-acetamido group and stabilizing the transition state., Williams SJ, Mark BL, Vocadlo DJ, James MN, Withers SG, J Biol Chem. 2002 Oct 18;277(42):40055-65. Epub 2002 Aug 8. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/12171933 12171933] |
[[Category: Beta-N-acetylhexosaminidase]] | [[Category: Beta-N-acetylhexosaminidase]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
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[[Category: tim barrel]] | [[Category: tim barrel]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Mar 20 12:37:10 2008'' |
Revision as of 10:37, 20 March 2008
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| , resolution 2.10Å | |||||||
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| Ligands: | , , and | ||||||
| Activity: | Beta-N-acetylhexosaminidase, with EC number 3.2.1.52 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
Wildtype Streptomyces plicatus beta-hexosaminidase in complex with product (GlcNAc)
Overview
SpHex, a retaining family 20 glycosidase from Streptomyces plicatus, catalyzes the hydrolysis of N-acetyl-beta-hexosaminides. Accumulating evidence suggests that the hydrolytic mechanism involves substrate-assisted catalysis wherein the 2-acetamido substituent acts as a nucleophile to form an oxazolinium ion intermediate. The role of a conserved aspartate residue (D313) in the active site of SpHex was investigated through kinetic and structural analyses of two variant enzymes, D313A and D313N. Three-dimensional structures of the wild-type and variant enzymes in product complexes with N-acetyl-d-glucosamine revealed substantial differences. In the D313A variant the 2-acetamido group was found in two conformations of which only one is able to aid in catalysis through anchimeric assistance. The mutation D313N results in a steric clash in the active site between Asn-313 and the 2-acetamido group preventing the 2-acetamido group from providing anchimeric assistance, consistent with the large reduction in catalytic efficiency and the insensitivity of this variant to chemical rescue. By comparison, the D313A mutation results in a shift in a shift in the pH optimum and a modest decrease in activity that can be rescued by using azide as an exogenous nucleophile. These structural and kinetic data provide evidence that Asp-313 stabilizes the transition states flanking the oxazoline intermediate and also assists to correctly orient the 2-acetamido group for catalysis. Based on analogous conserved residues in the family 18 chitinases and family 56 hyaluronidases, the roles played by the Asp-313 residue is likely general for all hexosaminidases using a mechanism involving substrate-assisted catalysis.
About this Structure
1M01 is a Single protein structure of sequence from Streptomyces plicatus. Full crystallographic information is available from OCA.
Reference
Aspartate 313 in the Streptomyces plicatus hexosaminidase plays a critical role in substrate-assisted catalysis by orienting the 2-acetamido group and stabilizing the transition state., Williams SJ, Mark BL, Vocadlo DJ, James MN, Withers SG, J Biol Chem. 2002 Oct 18;277(42):40055-65. Epub 2002 Aug 8. PMID:12171933
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