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1zct

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[[Image:1zct.gif|left|200px]]
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{{STRUCTURE_1zct| PDB=1zct | SCENE= }}
{{STRUCTURE_1zct| PDB=1zct | SCENE= }}
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'''structure of glycogenin truncated at residue 270 in a complex with UDP'''
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===structure of glycogenin truncated at residue 270 in a complex with UDP===
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==Overview==
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Glycogenin is a glycosyltransferase that functions as the autocatalytic initiator for the synthesis of glycogen in eukaryotic organisms. Prior structural work identified the determinants responsible for the recognition and binding of UDP-glucose and the catalytic manganese ion and implicated two aspartic acid residues in the reaction mechanism for self-glucosylation. We examined the effects of substituting asparagine and serine for the aspartic acid residues at positions 159 and 162. We also examined whether the truncation of the protein at residue 270 (delta270) was compatible with its structural integrity and its functional role as the initiator for glycogen synthesis. The truncated form of the enzyme was indistinguishable from the wild-type enzyme by all measures of activity and could support glycogen accumulation in a glycogenin-deficient yeast strain. Substitution of aspartate 159 by either serine or asparagine eliminated self-glucosylation and reduced trans-glucosylation activity by at least 260-fold but only reduced UDP-glucose hydrolytic activity by 4-14-fold. Substitution of aspartate 162 by either serine or asparagine eliminated self-glucosylation activity and reduced UDP-glucose hydrolytic activity by at least 190-fold. The trans-glucosylation of maltose was reduced to undetectable levels in the asparagine 162 mutant, whereas the serine 162 enzyme showed only an 18-30-fold reduction in its ability to trans-glucosylate maltose. These data support a role for aspartate 162 in the chemical step for the glucosyltransferase reaction and a role for aspartate 159 in binding and activating the acceptor molecule.
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The line below this paragraph, {{ABSTRACT_PUBMED_15849187}}, adds the Publication Abstract to the page
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(as it appears on PubMed at http://www.pubmed.gov), where 15849187 is the PubMed ID number.
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{{ABSTRACT_PUBMED_15849187}}
==About this Structure==
==About this Structure==
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[[Category: Zhou, J.]]
[[Category: Zhou, J.]]
[[Category: Glycosyltransferase]]
[[Category: Glycosyltransferase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 17:28:24 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 02:19:27 2008''

Revision as of 23:19, 28 July 2008

Image:1zct.png

Template:STRUCTURE 1zct

structure of glycogenin truncated at residue 270 in a complex with UDP

Template:ABSTRACT PUBMED 15849187

About this Structure

1ZCT is a Single protein structure of sequence from Oryctolagus cuniculus. Full crystallographic information is available from OCA.

Reference

Requirements for catalysis in mammalian glycogenin., Hurley TD, Stout S, Miner E, Zhou J, Roach PJ, J Biol Chem. 2005 Jun 24;280(25):23892-9. Epub 2005 Apr 22. PMID:15849187

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