1vzx
From Proteopedia
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| - | [[Image:1vzx.jpg|left|200px]]<br /><applet load="1vzx" size=" | + | [[Image:1vzx.jpg|left|200px]]<br /><applet load="1vzx" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1vzx, resolution 1.97Å" /> | caption="1vzx, resolution 1.97Å" /> | ||
'''ROLES OF ACTIVE SITE TRYPTOPHANS IN SUBSTRATE BINDING AND CATALYSIS BY ALPHA-1,3 GALACTOSYLTRANSFERASE'''<br /> | '''ROLES OF ACTIVE SITE TRYPTOPHANS IN SUBSTRATE BINDING AND CATALYSIS BY ALPHA-1,3 GALACTOSYLTRANSFERASE'''<br /> | ||
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==About this Structure== | ==About this Structure== | ||
| - | 1VZX is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bos_taurus Bos taurus] with MN, UDP and GOL as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Transferred_entry:_2.4.1.87 Transferred entry: 2.4.1.87], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.151 2.4.1.151] Known structural/functional Site: <scene name='pdbsite=AC1:Gol Binding Site For Chain B'>AC1</scene>. Full crystallographic information is available from [http:// | + | 1VZX is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bos_taurus Bos taurus] with <scene name='pdbligand=MN:'>MN</scene>, <scene name='pdbligand=UDP:'>UDP</scene> and <scene name='pdbligand=GOL:'>GOL</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Transferred_entry:_2.4.1.87 Transferred entry: 2.4.1.87], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.151 2.4.1.151] Known structural/functional Site: <scene name='pdbsite=AC1:Gol+Binding+Site+For+Chain+B'>AC1</scene>. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1VZX OCA]. |
==Reference== | ==Reference== | ||
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[[Category: transmembrane]] | [[Category: transmembrane]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Feb 3 10:17:38 2008'' |
Revision as of 08:17, 3 February 2008
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ROLES OF ACTIVE SITE TRYPTOPHANS IN SUBSTRATE BINDING AND CATALYSIS BY ALPHA-1,3 GALACTOSYLTRANSFERASE
Overview
Aromatic amino acids are frequent components of the carbohydrate binding, sites of lectins and enzymes. Previous structural studies have shown that, in alpha-1,3 galactosyltransferase, the binding site for disaccharide, acceptor substrates is encircled by four tryptophans, residues 249, 250, 314, and 356. To investigate their roles in enzyme specificity and, catalysis, we expressed and characterized variants of the catalytic domain, of alpha-1,3 galactosyltransferase with substitutions for each tryptophan., Substitution of glycine for tryptophan 249, whose indole ring interacts, with the nonpolar B face of glucose or GlcNAc, greatly increases the K(m), for the acceptor substrate. In contrast, the substitution of tyrosine for, tryptophan 314, which interacts with the beta-galactosyl moiety of the, acceptor and UDP-galactose, decreases k(cat) for the galactosyltransferase, reaction but does not affect the low UDP-galactose hydrolase activity., Thus, this highly conserved residue stabilizes the transition state for, the galactose transfer to disaccharide but not to water. High-resolution, crystallographic structures of the Trp(249)Gly mutant and the Trp(314)Tyr, mutant indicate that the mutations do not affect the overall structure of, the enzyme or its interactions with ligands. Substitutions for tryptophan, 250 have only small effects on catalytic activity, but mutation of, tryptophan 356 to threonine reduces catalytic activity for both, transferase and hydrolase activities and reduces affinity for the acceptor, substrate. This residue is adjacent to the flexible C-terminus that, becomes ordered on binding UDP to assemble the acceptor binding site and, influence catalysis. The results highlight the diverse roles of these, tryptophans in enzyme action and the importance of k(cat) changes in, modulating glycosyltransferase specificity.
About this Structure
1VZX is a Single protein structure of sequence from Bos taurus with , and as ligands. Active as Transferred entry: 2.4.1.87, with EC number 2.4.1.151 Known structural/functional Site: . Full crystallographic information is available from OCA.
Reference
Roles of active site tryptophans in substrate binding and catalysis by alpha-1,3 galactosyltransferase., Zhang Y, Deshpande A, Xie Z, Natesh R, Acharya KR, Brew K, Glycobiology. 2004 Dec;14(12):1295-302. Epub 2004 Jun 30. PMID:15229192
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