Microenvironmental Properties and Conformational Changes in Glycogen Phosphorylase

1985 ◽  
pp. 149-163
Author(s):  
A. E. Evangelopoulos
Keyword(s):  
Conformational Changes ◽  
Glycogen Phosphorylase

scholarly journals Allosteric interactions of glycogen phosphorylase b. A crystallographic study of glucose 6-phosphate and inorganic phosphate binding to di-imidate-cross-linked phosphorylase b

1984 ◽  
Vol 218 (1) ◽  
pp. 45-60 ◽  
Author(s):  
A Lorek ◽  
K S Wilson ◽  
M S P Sansom ◽  
D I Stuart ◽  
E A Stura ◽  
...  
Keyword(s):  
Binding Site ◽  
Conformational Changes ◽  
Inorganic Phosphate ◽  
Glycogen Phosphorylase ◽  
Phosphate Binding ◽  
Binding Studies ◽  
Structural Explanation ◽  
Alpha Helices ◽  
Allosteric Effector ◽  
Glycogen Phosphorylase B

The binding to glycogen phosphorylase b of glucose 6-phosphate and inorganic phosphate (respectively allosteric inhibitor and substrate/activator of the enzyme) were studied in the crystal at 0.3 nm (3A) resolution. Glucose 6-phosphate binds in the alpha-configuration at a site that is close to the AMP allosteric effector site at the subunit-subunit interface and promotes several conformational changes. The phosphate-binding site of the enzyme for glucose 6-phosphate involves contacts to two cationic residues, Arg-309 and Lys-247. This site is also occupied in the inorganic-phosphate-binding studies and is therefore identified as a high-affinity phosphate-binding site. It is distinct from the weaker phosphate-binding site of the enzyme for AMP, which is 0.27 nm (2.7A) away. The glucose moiety of glucose 6-phosphate and the adenosine moiety of AMP do not overlap. The results provide a structural explanation for the kinetic observations that glucose 6-phosphate inhibition of AMP activation of phosphorylase b is partially competitive and highly co-operative. The results suggest that the transmission of allosteric conformational changes involves an increase in affinity at phosphate-binding sites and relative movements of alpha-helices. In order to study glucose 6-phosphate and phosphate binding it was necessary to cross-link the crystals. The use of dimethyl malondi-imidate as a new cross-linking reagent in protein crystallography is discussed.

Protein kinases and their therapeutic exploitation

2007 ◽  
Vol 35 (1) ◽  
pp. 7-11 ◽  
Author(s):  
L. Johnson
Keyword(s):  
Protein Kinases ◽  
Conformational Changes ◽  
Glycogen Phosphorylase ◽  
Molecular Level ◽  
Enzyme Activation ◽  
Phosphorylase Kinase ◽  
Binding Properties ◽  
Cyclin Dependent Kinases ◽  
Substrate Protein ◽  
Potential Therapeutic Application

This review focuses on the recognition properties of protein kinases at the molecular level. Phosphorylation of the substrate protein by a protein kinase can result in enzyme activation or inhibition, conformational changes that change recognition properties, or the creation of a surface with distinct binding properties. Protein kinases have become important targets for the development of inhibitors with potential therapeutic application. Various examples are considered in this review, and I discuss our own work on glycogen phosphorylase and phosphorylase kinase, and the structures of proteins involved with the cell cycle, including cyclins and cyclin-dependent kinases.

scholarly journals The binding of d-gluconohydroximo-1,5-lactone to glycogen phosphorylase. Kinetic, ultracentrifugation and crystallographic studies

1991 ◽  
Vol 274 (2) ◽  
pp. 329-338 ◽  
Author(s):  
A C Papageorgiou ◽  
N G Oikonomakos ◽  
D D Leonidas ◽  
B Bernet ◽  
D Beer ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Glycogen Phosphorylase ◽  
Glycogen Synthesis ◽  
Chair Conformation ◽  
Catalytic Site ◽  
Crystallization Experiments ◽  
Density Map ◽  
Beta Glucosidase ◽  
Electron Density Map ◽  
T State

Combined kinetic, ultracentrifugation and X-ray-crystallographic studies have characterized the effect of the beta-glucosidase inhibitor gluconohydroximo-1,5-lactone on the catalytic and structural properties of glycogen phosphorylase. In the direction of glycogen synthesis, gluconohydroximo-1,5-lactone was found to competitively inhibit both the b (Ki 0.92 mM) and the alpha form of the enzyme (Ki 0.76 mM) with respect to glucose 1-phosphate in synergism with caffeine. In the direction of glycogen breakdown, gluconohydroximo-1,5-lactone was found to inhibit phosphorylase b in a non-competitive mode with respect to phosphate, and no synergism with caffeine could be demonstrated. Ultracentrifugation and crystallization experiments demonstrated that gluconohydroximo-1,5-lactone was able to induce dissociation of tetrameric phosphorylase alpha and stabilization of the dimeric T-state conformation. A crystallographic binding study with 100 mM-gluconohydroximo-1,5-lactone at 0.24 nm (2.4 A) resolution showed a major peak at the catalytic site, and no significant conformational changes were observed. Analysis of the electron-density map indicated that the ligand adopts a chair conformation. The results are discussed with reference to the ability of the catalytic site of the enzyme to distinguish between two or more conformations of the glucopyranose ring.

Fluorescence Quenching, a Tool for Probing Conformational Changes in Glycogen Phosphorylase

1973 ◽  
Vol 51 (4) ◽  
pp. 344-356 ◽  
Author(s):  
K. O. Honikel ◽  
N. B. Madsen
Keyword(s):  
Fluorescence Quenching ◽  
Conformational Changes ◽  
Glycogen Phosphorylase ◽  
Pyridoxal Phosphate ◽  
Catalytic Mechanism ◽  
Fluorescence Emission ◽  
Ring Structure ◽  
Rabbit Muscle ◽  
Quenching Rate ◽  
Muscle Phosphorylase

This study shows that conformational changes in glycogen phosphorylase are accompanied by changes in the accessibility of tryptophan residues and of the coenzyme, pyridoxal phosphate, to the surrounding aqueous medium. The accessibility was estimated by determining the extent to which iodide can quench the fluorescence emission of these moieties by colliding with them, since iodide cannot collide with a buried chromophore and hence cannot quench its fluorescence. Rabbit muscle phosphorylase b, its apoform, and phosphorylase a exhibit differences in the number of exposed tryptophans, while the phosphorylase b forms from rabbit skeletal muscle and pig heart also show differences.Differences are also observed in the accessibility of the coenzyme in different forms of the enzyme. The quenching rate constant, a measure of accessibility, differs for phosphorylases a and b, and this constant is affected differently by ligand binding to the two forms. While the allosteric inhibitors, ATP and glucose 6-phosphate, render the pyridoxal phosphate moiety of phosphorylase b more accessible, the activator, AMP, and substrate, glucose 1-phosphate, together cause it to be totally inaccessible to fluorescence quenching by iodide. AMP and glucose 1-phosphate appear to mediate a conformational change which buries the coenzyme. While pyridoxal phosphate is necessary for catalytic activity, one may conclude from these experiments that its ring structure is unlikely to participate directly in the catalytic mechanism.

scholarly journals Effect of Arginine on Chaperone-Like Activity of HspB6 and Monomeric 14-3-3ζ

2020 ◽  
Vol 21 (6) ◽  
pp. 2039 ◽  
Author(s):  
Valeriya V. Mikhaylova ◽  
Tatiana B. Eronina ◽  
Natalia A. Chebotareva ◽  
Vladimir V. Shubin ◽  
Daria I. Kalacheva ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Glycogen Phosphorylase ◽  
Test System ◽  
Monomeric Form ◽  
Thermal Aggregation ◽  
Scanning Calorimetry ◽  
Glycogen Phosphorylase B ◽  
Protein Chaperones ◽  
Aggregation Activity ◽  
Thermal Stability Of

The effect of protein chaperones HspB6 and the monomeric form of the protein 14-3-3ζ (14-3-3ζm) on a test system based on thermal aggregation of UV-irradiated glycogen phosphorylase b (UV-Phb) at 37 °C and a constant ionic strength (0.15 M) was studied using dynamic light scattering. A significant increase in the anti-aggregation activity of HspB6 and 14-3-3ζm was demonstrated in the presence of 0.1 M arginine (Arg). To compare the effects of these chaperones on UV-Phb aggregation, the values of initial stoichiometry of the chaperone–target protein complex (S0) were used. The analysis of the S0 values shows that in the presence of Arg fewer chaperone subunits are needed to completely prevent aggregation of the UV-Phb subunit. The changes in the structures of HspB6 and 14-3-3ζm induced by binding of Arg were evaluated by the fluorescence spectroscopy and differential scanning calorimetry. It was suggested that Arg caused conformational changes in chaperone molecules, which led to a decrease in the thermal stability of protein chaperones and their destabilization.

Conformational changes and the mechanism of resolution of glycogen phosphorylase

Biochemistry ◽  
1969 ◽  
Vol 8 (6) ◽  
pp. 2422-2429 ◽  
Author(s):  
Jerry L. Hedrick ◽  
Shmuel Shaltiel ◽  
Edmond H. Fischer
Keyword(s):  
Conformational Changes ◽  
Glycogen Phosphorylase

Conformational Changes in Glycogen Phosphorylase Studied with a Spin-Label Probe

1976 ◽  
Vol 61 (1) ◽  
pp. 237-242 ◽  
Author(s):  
John R. GRIFFITHS ◽  
Raymond A. DWEK ◽  
George K. RADDA
Keyword(s):  
Conformational Changes ◽  
Spin Label ◽  
Glycogen Phosphorylase ◽  
Label Probe

Influence of Calcium Ions on the Plant Cell Surface: Membrane Fusions and Conformational Changes

1974 ◽  
Vol 32 ◽  
pp. 154-155
Author(s):  
D. James Morré ◽  
Charles E. Bracker ◽  
William J. VanDerWoude
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Conformational Changes ◽  
Calcium Ions ◽  
Surface Membrane ◽  
Carboxyl Groups ◽  
Cross Linking ◽  
Ultrastructural Evidence ◽  
Glycine Max L ◽  
Wall Extensibility

Calcium ions in the concentration range 5-100 mM inhibit auxin-induced cell elongation and wall extensibility of plant stems. Inhibition of wall extensibility requires that the tissue be living; growth inhibition cannot be explained on the basis of cross-linking of carboxyl groups of cell wall uronides by calcium ions. In this study, ultrastructural evidence was sought for an interaction of calcium ions with some component other than the wall at the cell surface of soybean (Glycine max (L.) Merr.) hypocotyls.

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