scholarly journals Conformational changes induced by polyanions in haemoglobin from Camelus dromedarius. Studies on the ferric derivatives

1986 ◽  
Vol 235 (3) ◽  
pp. 791-795 ◽  
Author(s):  
R Santucci ◽  
F Ascoli ◽  
G Amiconi ◽  
M Brunori
Keyword(s):  
Spin State ◽  
Conformational Changes ◽  
Binding Sites ◽  
Camelus Dromedarius ◽  
Inositol Hexakisphosphate ◽  
Protein Conformational Changes ◽  
T State ◽  
Redox Equilibria ◽  
Derivatives Of

The effect of inositol hexakisphosphate on the redox equilibria and on the c.d. spectra of ferric derivatives of haemoglobin from Camelus dromedarius has shown that: two distinct functionally relevant binding sites for polyanions are present on the protein; conformational changes promoted by inositol hexakisphosphate are largely dependent on spin state of the iron; tertiary and quaternary changes are not necessarily linked; structures induced by polyanions can be mixed forms that are neither T-state nor R-state.

scholarly journals Conformational changes induced by polyanions in haemoglobin from Camelus dromedarius. Circular-dichroism study on the oxy derivative

1985 ◽  
Vol 231 (3) ◽  
pp. 793-796 ◽  
Author(s):  
R Santucci ◽  
F Ascoli ◽  
G Amiconi ◽  
A Bertollini ◽  
M Brunori
Keyword(s):  
Functional Properties ◽  
Conformational Changes ◽  
Direct Evidence ◽  
Tertiary Structure ◽  
Camelus Dromedarius ◽  
Local Change ◽  
Inositol Hexakisphosphate ◽  
Human Haemoglobin ◽  
Circular Dichroïsm ◽  
O2 Binding

The c.d. spectrum of oxyhaemoglobin from Camelus dromedarius is significantly affected by the presence of inositol hexakisphosphate. Correlation with O2-binding measurements shows that these dichroic changes parallel the functional properties of the protein. The optical modifications suggest that, in contrast with human haemoglobin, the conformational changes induced by inositol hexakisphosphate on dromedary oxyhaemoglobin are mainly attributable to a local change of the tertiary structure reminiscent of that of the deoxy derivative, the quaternary conformation seeming to be almost unaffected. The results provide direct evidence of the existence on the protein of two distinct sites for polyanions.

scholarly journals Conformational changes induced by polyanions in haemoglobin from the dromedary (Camelus dromedarius) Role of chloride ions

1986 ◽  
Vol 240 (2) ◽  
pp. 613-616 ◽  
Author(s):  
R Santucci ◽  
G Amiconi ◽  
F Ascoli ◽  
M Brunori
Keyword(s):  
Conformational Changes ◽  
Functional Data ◽  
Tertiary Structure ◽  
Chloride Ions ◽  
Camelus Dromedarius ◽  
Dextran Sulphate ◽  
Inositol Hexakisphosphate ◽  
Midpoint Potential ◽  
Physiological Value

The role of chloride ions in modulating polyanion-induced conformational changes in haemoglobin from the dromedary (Camelus dromedarius) has been investigated. The results obtained have shown that: in the ferric derivative at pH 6.5 the effect of single polyanion (dextran sulphate and inositol hexakisphosphate) on the conformation is essentially local, thus involving only the tertiary structure of the protein; the presence of chloride ions at a concentration close to the physiological value (i.e. 150 mM) is essential to induce quaternary conformational changes in the polyanion-ferric protein system; comparison between structural and functional data correlates polyanion-induced tertiary conformational changes with changes in the value of midpoint potential, E'0, and quaternary changes with co-operativity.

Analysis of the surface topography of glycogen phosphorylase a: implications for metabolic interconversion and regulatory mechanisms

1979 ◽  
Vol 57 (6) ◽  
pp. 789-797 ◽  
Author(s):  
R. J. Fletterick ◽  
S. Sprang ◽  
N. B. Madsen
Keyword(s):  
Surface Topography ◽  
Conformational Changes ◽  
Binding Sites ◽  
Pyridoxal Phosphate ◽  
Glycogen Storage ◽  
Enzymic Activity ◽  
Phosphate Binding ◽  
Active Centers ◽  
Large Molecular Weight ◽  
T State

Computer drawings of the van der Waals contours of atoms on the surface represent the phosphorylase molecule at 2.5 Å (1 Å = 0.1 nm) resolution with color coding for acidic and basic residues, bound ligands, or conformational changes. The asymmetry resulting from the twofold axis of each dimer provides two faces which can be distinguished structurally and functionally. Thus, a concave catalytic face contains the glycogen storage sites on its periphery with entrances to the glucose-1-phosphate binding sites of the active centers, adjacent to the pyridoxal phosphate moieties, near its center. Just outside the active site is a binding site for negative effectors such as caffeine. On the side of the dimer opposite to the catalytic face is found a convex control face containing the binding sites for the allosteric activator AMP, for which ATP also competes. Quite close to these sites are found the Ser-14-phosphates hydrogen bonded to Arg-69 and Arg-43′ of the symmetry-related monomer. Each Ser-14-phosphate is surrounded by positive charges, including more than are found on adjacent sequences, and therefore, comparative studies on peptides cannot describe fully the specificity and binding requirements of the kinase and phosphatase.The surface topography of the glucose stabilized T state (taut) and the changes which occur during the allosteric transitions induced by AMP and substrates are discussed in terms of their functional implications for the control of both the intrinsic enzymic activity and of the metabolic interconversions between the a and b forms. In particular, the two conformational states (taut and relaxed) exhibit different structural arrangements of the binding sites for the negative effector, caffeine, and the positive effector, AMP. Linkage between the various effector sites is demonstrated by conformational changes in the surface topography. Since the control face is opposite to the catalytic face, the interconverting enzymes can bind to, and act on, the phosphorylase while the latter is bound to glycogen. The Ser-14 residues are only 40 Å apart across the control face and could be bridged readily by the multimeric kinase (α4β4γ4δ4, 1 300 000 daltons) or the large molecular weight form of the phosphatase. The T →R conformational change causes the Ser-14-phosphate to move 5 Å in from the surface, which may be related to the 20-fold decrease of the phosphatase Vm with unchanged Km.

scholarly journals Protein conformational changes and myelin solubilization by anion-detergent solutions

FEBS Letters ◽  
1992 ◽  
Vol 309 (3) ◽  
pp. 376-380 ◽  
Author(s):  
Jaime Monreal ◽  
Pedro Carmona ◽  
Pilar Regueiro ◽  
Ricardo S. Diaz
Keyword(s):  
Conformational Changes ◽  
Protein Conformational Changes ◽  
Detergent Solutions
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