1zct: Difference between revisions

Revision as of 17:14, 21 February 2008

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

OverviewOverview

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.

About this StructureAbout this Structure

1ZCT is a Single protein structure of sequence from Oryctolagus cuniculus with and as ligands. Active as Glycogenin glucosyltransferase, with EC number 2.4.1.186 Full crystallographic information is available from OCA.

ReferenceReference

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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-[[Image:1zct.gif|left|200px]]<br /><applet load="1zct" size="450" color="white" frame="true" align="right" spinBox="true"
+[[Image:1zct.gif|left|200px]]<br /><applet load="1zct" size="350" color="white" frame="true" align="right" spinBox="true"
 caption="1zct, resolution 2.600&Aring;" />
 '''structure of glycogenin truncated at residue 270 in a complex with UDP'''<br />
 ==Overview==
-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.
+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.
 ==About this Structure==
-ZCT is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Oryctolagus_cuniculus Oryctolagus cuniculus] with MN and UDP as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Glycogenin_glucosyltransferase Glycogenin glucosyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.186 2.4.1.186] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1ZCT OCA].
+ZCT is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Oryctolagus_cuniculus Oryctolagus cuniculus] with <scene name='pdbligand=MN:'>MN</scene> and <scene name='pdbligand=UDP:'>UDP</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Glycogenin_glucosyltransferase Glycogenin glucosyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.186 2.4.1.186] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1ZCT OCA].
 ==Reference==
@@ Line 14: / Line 14: @@
 [[Category: Oryctolagus cuniculus]]
 [[Category: Single protein]]
-[[Category: Hurley, T.D.]]
+[[Category: Hurley, T D.]]
 [[Category: Miner, E.]]
-[[Category: Roach, P.J.]]
+[[Category: Roach, P J.]]
-[[Category: Stout, S.L.]]
+[[Category: Stout, S L.]]
 [[Category: Zhou, J.]]
 [[Category: MN]]
@@ Line 23: / Line 23: @@
 [[Category: glycosyltransferase]]
-''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Wed Nov 21 07:23:23 2007''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:14:19 2008''