1hp4
From Proteopedia
(New page: 200px<br /><applet load="1hp4" size="450" color="white" frame="true" align="right" spinBox="true" caption="1hp4, resolution 2.20Å" /> '''CRYSTAL STRUCTURE OF...) |
|||
| Line 1: | Line 1: | ||
| - | [[Image:1hp4.jpg|left|200px]]<br /><applet load="1hp4" size=" | + | [[Image:1hp4.jpg|left|200px]]<br /><applet load="1hp4" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1hp4, resolution 2.20Å" /> | caption="1hp4, resolution 2.20Å" /> | ||
'''CRYSTAL STRUCTURE OF STREPTOMYCES PLICATUS BETA-N-ACETYLHEXOSAMINIDASE'''<br /> | '''CRYSTAL STRUCTURE OF STREPTOMYCES PLICATUS BETA-N-ACETYLHEXOSAMINIDASE'''<br /> | ||
==Overview== | ==Overview== | ||
| - | beta-Hexosaminidase, a family 20 glycosyl hydrolase, catalyzes the removal | + | beta-Hexosaminidase, a family 20 glycosyl hydrolase, catalyzes the removal of beta-1,4-linked N-acetylhexosamine residues from oligosaccharides and their conjugates. Heritable deficiency of this enzyme results in various forms of GalNAc-beta(1,4)-[N-acetylneuraminic acid (2,3)]-Gal-beta(1,4)-Glc-ceramide gangliosidosis, including Tay-Sachs disease. We have determined the x-ray crystal structure of a beta-hexosaminidase from Streptomyces plicatus to 2.2 A resolution (Protein Data Bank code ). beta-Hexosaminidases are believed to use a substrate-assisted catalytic mechanism that generates a cyclic oxazolinium ion intermediate. We have solved and refined a complex between the cyclic intermediate analogue N-acetylglucosamine-thiazoline and beta-hexosaminidase from S. plicatus to 2.1 A resolution (Protein Data Bank code ). Difference Fourier analysis revealed the pyranose ring of N-acetylglucosamine-thiazoline bound in the enzyme active site with a conformation close to that of a (4)C(1) chair. A tryptophan-lined hydrophobic pocket envelopes the thiazoline ring, protecting it from solvolysis at the iminium ion carbon. Within this pocket, Tyr(393) and Asp(313) appear important for positioning the 2-acetamido group of the substrate for nucleophilic attack at the anomeric center and for dispersing the positive charge distributed into the oxazolinium ring upon cyclization. This complex provides decisive structural evidence for substrate-assisted catalysis and the formation of a covalent, cyclic intermediate in family 20 beta-hexosaminidases. |
==About this Structure== | ==About this Structure== | ||
| - | 1HP4 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Streptomyces_plicatus Streptomyces plicatus] with CL, SO4 and GOL 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:// | + | 1HP4 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Streptomyces_plicatus Streptomyces plicatus] with <scene name='pdbligand=CL:'>CL</scene>, <scene name='pdbligand=SO4:'>SO4</scene> and <scene name='pdbligand=GOL:'>GOL</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=1HP4 OCA]. |
==Reference== | ==Reference== | ||
| Line 14: | Line 14: | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Streptomyces plicatus]] | [[Category: Streptomyces plicatus]] | ||
| - | [[Category: Mark, B | + | [[Category: Mark, B L.]] |
[[Category: CL]] | [[Category: CL]] | ||
[[Category: GOL]] | [[Category: GOL]] | ||
| Line 25: | Line 25: | ||
[[Category: x-ray]] | [[Category: x-ray]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:03:29 2008'' |
Revision as of 11:03, 21 February 2008
|
CRYSTAL STRUCTURE OF STREPTOMYCES PLICATUS BETA-N-ACETYLHEXOSAMINIDASE
Overview
beta-Hexosaminidase, a family 20 glycosyl hydrolase, catalyzes the removal of beta-1,4-linked N-acetylhexosamine residues from oligosaccharides and their conjugates. Heritable deficiency of this enzyme results in various forms of GalNAc-beta(1,4)-[N-acetylneuraminic acid (2,3)]-Gal-beta(1,4)-Glc-ceramide gangliosidosis, including Tay-Sachs disease. We have determined the x-ray crystal structure of a beta-hexosaminidase from Streptomyces plicatus to 2.2 A resolution (Protein Data Bank code ). beta-Hexosaminidases are believed to use a substrate-assisted catalytic mechanism that generates a cyclic oxazolinium ion intermediate. We have solved and refined a complex between the cyclic intermediate analogue N-acetylglucosamine-thiazoline and beta-hexosaminidase from S. plicatus to 2.1 A resolution (Protein Data Bank code ). Difference Fourier analysis revealed the pyranose ring of N-acetylglucosamine-thiazoline bound in the enzyme active site with a conformation close to that of a (4)C(1) chair. A tryptophan-lined hydrophobic pocket envelopes the thiazoline ring, protecting it from solvolysis at the iminium ion carbon. Within this pocket, Tyr(393) and Asp(313) appear important for positioning the 2-acetamido group of the substrate for nucleophilic attack at the anomeric center and for dispersing the positive charge distributed into the oxazolinium ring upon cyclization. This complex provides decisive structural evidence for substrate-assisted catalysis and the formation of a covalent, cyclic intermediate in family 20 beta-hexosaminidases.
About this Structure
1HP4 is a Single protein structure of sequence from Streptomyces plicatus with , and as ligands. Active as Beta-N-acetylhexosaminidase, with EC number 3.2.1.52 Full crystallographic information is available from OCA.
Reference
Crystallographic evidence for substrate-assisted catalysis in a bacterial beta-hexosaminidase., Mark BL, Vocadlo DJ, Knapp S, Triggs-Raine BL, Withers SG, James MN, J Biol Chem. 2001 Mar 30;276(13):10330-7. Epub 2000 Dec 21. PMID:11124970
Page seeded by OCA on Thu Feb 21 13:03:29 2008
