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| - | ==Overview==
| + | {{ABSTRACT_2106586}} |
| - | The crystal structure of phosphorylase b-heptulose 2-phosphate complex with oligosaccharide and AMP bound has been refined by molecular dynamics and crystallographic least-squares with the program XPLOR. Shifts in atomic positions of up to 4 A from the native enzyme structure were correctly determined by the program without manual intervention. The final crystallographic R value for data between 8 and 2.86 A resolution is 0.201, and the overall root-mean-square difference between the native and complexed structure is 0.58 A for all protein atoms. The results confirm the previous observation that there is a direct hydrogen bond between the phosphate of heptulose 2-phosphate and the pyridoxal phosphate 5'-phosphate group. The close proximity of the two phosphates is stabilized by an arginine residue, Arg569, which shifts from a site buried in the protein to a position where it can make contact with the product phosphate. There is a mutual interchange in position between the arginine and an acidic group, Asp283. These movements represent the first stage of the allosteric response which converts the catalytic site from a low to a high-affinity binding site. Communication of these changes to other sites is prevented in the crystal by the lattice forces, which also form the subunit interface. The constellation of groups in the phosphorylase transition state analogue complex provides a structural basis for understanding the catalytic mechanism in which the cofactor pyridoxal phosphate 5'-phosphate group functions as a general acid to promote attack by the substrate phosphate on the glycosidic bond when the reaction proceeds in the direction of glycogen degradation. In the direction of glycogen synthesis, stereoelectronic effects contribute to the cleavage of the C-1-O-1 bond. In both reactions the substrate phosphate plays a key role in transition state stabilization. The details of the oligosaccharide, maltoheptaose, interactions with the enzyme at the glycogen storage site are also described.
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| | ==About this Structure== | | ==About this Structure== |
| | 6GPB is a [[Single protein]] structure. The following page contains interesting information on the relation of 6GPB with [[http://pdb.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb24_1.html Glycogen Phosphorylase]]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6GPB OCA]. | | 6GPB is a [[Single protein]] structure. The following page contains interesting information on the relation of 6GPB with [[http://pdb.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb24_1.html Glycogen Phosphorylase]]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6GPB OCA]. |
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| - | ==Reference== | |
| - | Refined crystal structure of the phosphorylase-heptulose 2-phosphate-oligosaccharide-AMP complex., Johnson LN, Acharya KR, Jordan MD, McLaughlin PJ, J Mol Biol. 1990 Feb 5;211(3):645-61. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/2106586 2106586] | |
| | [[Category: Glycogen Phosphorylase]] | | [[Category: Glycogen Phosphorylase]] |
| | [[Category: Phosphorylase]] | | [[Category: Phosphorylase]] |
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| | [[Category: Johnson, L N.]] | | [[Category: Johnson, L N.]] |
| | [[Category: Glycogen phosphorylase]] | | [[Category: Glycogen phosphorylase]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 22:40:46 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Jun 26 18:30:33 2008'' |
Revision as of 15:30, 26 June 2008
Template:STRUCTURE 6gpb
REFINED CRYSTAL STRUCTURE OF THE PHOSPHORYLASE-HEPTULOSE 2-PHOSPHATE-OLIGOSACCHARIDE-AMP COMPLEX
Template:ABSTRACT 2106586
About this Structure
6GPB is a Single protein structure. The following page contains interesting information on the relation of 6GPB with [Glycogen Phosphorylase]. Full crystallographic information is available from OCA.
Page seeded by OCA on Thu Jun 26 18:30:33 2008
