scholarly journals Cytoplasmic interactions between phospholamban residues 1–20 and the calcium-activated ATPase of the sarcoplasmic reticulum

2001 ◽  
Vol 355 (3) ◽  
pp. 699-706 ◽  
Author(s):  
Parveen SHARMA ◽  
Valerie B. PATCHELL ◽  
Yuan GAO ◽  
James S. EVANS ◽  
Barry A. LEVINE
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Tryptophan Fluorescence ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Fluorescence Studies ◽  
Cytoplasmic Region ◽  
Spectral Changes ◽  
Conformational Effects ◽  
Intrinsic Tryptophan Fluorescence ◽  
Nmr Study ◽  
Phosphorylated Peptide

Phospholamban regulates the activity of the calcium-activated ATPase (CaATPase) of cardiac sarcoplasmic reticulum. Equilibrium fluorescence studies have shown that the N-terminal cytoplasmic region of phospholamban (residues 1–20, domain 1) causes a decrease in the intrinsic tryptophan fluorescence of the CaATPase. The interaction of phospholamban residues 1–20 with the CaATPase also results in spectral changes for the extrinsic chromophore FITC covalently attached to the cytoplasmic region of the calcium pump. The fluorescence changes for both reporter groups correlate with a dissociation constant of ≈ 40µM for the complex between phospholamban residues 1–20 and the CaATPase. Complex formation is notably weaker when phospholamban 1–20 is titrated into the CaATPase in the presence of calcium, with altered conformational effects resulting from binding. The interaction of domain 1 of phospholamban with the CaATPase is also reduced upon phosphorylation of phospholamban 1–20 at Ser-16. This region of phospholamban 1–20 is shown by isotope-edited NMR study to be involved in interaction with the CaATPase. Binding of the phosphorylated peptide is not abolished, however, indicating that phospholamban 1–20 remains associated with the CaATPase even after phosphorylation. The data provide direct evidence for the interaction between the cytoplasmic regions of phospholamban and the pump, and are discussed in the context of the mechanism for inhibition of cardiac CaATPase activity by phospholamban.

scholarly journals Inactivation of sarcoplasmic-reticulum Ca2+-ATPase in low-frequency-stimulated muscle results from a modification of the active site

1992 ◽  
Vol 285 (1) ◽  
pp. 303-309 ◽  
Author(s):  
S Matsushita ◽  
D Pette
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Active Site ◽  
Low Frequency ◽  
Fluorescein Isothiocyanate ◽  
Tryptophan Fluorescence ◽  
Atp Binding ◽  
Binding Characteristics ◽  
Intrinsic Tryptophan Fluorescence ◽  
Inactive Form ◽  
Induced Changes

Molecular changes underlying the partial inactivation of the sarcoplasmic-reticulum (SR) Ca(2+-) ATPase in low-frequency-stimulated fast-twitch muscle were investigated in the present study. The specific Ca(2+)-ATPase activity, as well as the ATP- and acetyl phosphate-driven Ca2+ uptakes by the SR, were reduced by approx. 30% in 4-day-stimulated muscle. Phosphoprotein formation of the enzyme in the presence of ATP or Pi was also decreased to the same extent. Measurements of ATP binding revealed a 30% decrease in binding to the enzyme. These changes were accompanied by similar decreases in the ligand-induced (ATP, ADP, Pi) intrinsic tryptophan fluorescence. A decreased binding of fluorescein isothiocyanate (FITC) corresponded to the lower ATP binding and phosphorylation of the enzyme. Moreover, Pi-induced changes in fluorescence of the FITC-labelled enzyme did not differ between SR from stimulated and contralateral muscles, indicating that Ca(2+)- ATPase molecules which did not bind FITC were responsible for the decreased Pi-dependent phosphorylation, and therefore represented the inactive form of the enzyme. No differences existed between the Ca(2+)-induced changes in the intrinsic fluorescence of SR from stimulated and contralateral muscles which fit their similar Ca(2+)-binding characteristics. Taking the proposed architecture of the Ca2(+)-ATPase into consideration, our results suggest that the inactivation relates to a circumscribed structural alteration of the enzyme in sections of the active site consisting of the nucleotide-binding and phosphorylation domains.

scholarly journals Apohorseradish Peroxidase Unfolding and Refolding: Intrinsic Tryptophan Fluorescence Studies

1999 ◽  
Vol 76 (1) ◽  
pp. 443-450 ◽  
Author(s):  
Mauricio Lasagna ◽  
Enrico Gratton ◽  
David M. Jameson ◽  
Juan E. Brunet
Keyword(s):  
Tryptophan Fluorescence ◽  
Fluorescence Studies ◽  
Intrinsic Tryptophan Fluorescence

scholarly journals Fluorescence studies on the nucleotide- and Ca2+-binding domains of molluscan myosin

1985 ◽  
Vol 231 (1) ◽  
pp. 31-38 ◽  
Author(s):  
C Wells ◽  
K E Warriner ◽  
C R Bagshaw
Keyword(s):  
Atpase Activity ◽  
Specific Binding ◽  
Neck Region ◽  
Tryptophan Fluorescence ◽  
Regulatory Domain ◽  
Fluorescence Studies ◽  
Tryptic Fragment ◽  
Binding Domains ◽  
Intrinsic Tryptophan Fluorescence ◽  
Molluscan Species

The effects of nucleotides and Ca2+ on the intrinsic tryptophan fluorescence of molluscan myosin and its proteolytic fragments were studied. By using these proteins from the scallop, Pecten maximus, the existence of two distinct tryptophan-containing domains was established, which respond independently to ATP and Ca2+-specific binding. The latter is located in the ‘neck’ region of the myosin, which constitutes the regulatory domain. Subfragment 1, lacking the regulatory domain, responded only to ATP binding. On the other hand a tryptic fragment comprising the regulatory domain responded only to Ca2+ binding. Subfragment 1, containing the regulatory domain, responded to both ATP and Ca2+, but its ATPase activity was Ca2+-insensitive. By contrast, the ATPase activity of HMM was Ca2+-sensitive. Increasing the ionic strength had a detrimental effect on Ca2+-sensitivity, and fluorescence studies on solubilized myosin were therefore of limited value. Myosin and its fragments from other molluscan species which were investigated produced similar changes to those of Pectan maximus.

The Influence of Detergents on the Ca2+-and Mg2+-Dependent Adenosine Triphosphatase of the Sarcoplasmic Reticulum

1982 ◽  
Vol 37 (3-4) ◽  
pp. 299-307 ◽  
Author(s):  
Hans Lüdi ◽  
Bernhard Rauch ◽  
Wilhelm Hasselbach
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Ions ◽  
Inorganic Phosphate ◽  
Adenosine Triphosphatase ◽  
Tryptophan Fluorescence ◽  
The Other ◽  
Phosphorylated Protein ◽  
Intrinsic Tryptophan Fluorescence ◽  
Low Concentrations ◽  
Calcium Affinity

Abstract During the stepwise solubilization of sarcoplasmic reticulum vesicles with detergents, the following changes in the structural and enzymatic properties of the preparation are observed: 1. The viscosity of the vesicular suspension initially rises. This change is accompanied by the formation of elongated tubules. Subsequently the membranes are completely desintegrated, resulting in a considerable reduction of the viscosity. 2. A decrease in the activity of the Ca2+-dependent ATPase, which is restored after complete solubilization. 3. A decrease in the change of intrinsic tryptophan-fluorescence on removal of calcium ions, which is also restored after complete solubilization. 4. A decrease of the calcium affinity of the ATPase. 5. A decrease in the amount of phosphorylated protein formed by the incorporation of inorganic phosphate. On the other hand, the amount of phosphoprotein formed from ATP is not affected during solubilization. 6. The dependence of the initial rates of phosphoprotein formation from inorganic phosphate on either magnesium or inorganic phosphate at low concentrations of the respective ligand changes from an S-shape profile to a normal hyperbolic profile after solubilization.

A Reproducible Selective Stain for Cardiac Sarcoplasmic Reticulum

1974 ◽  
Vol 32 ◽  
pp. 214-215
Author(s):  
R. A. Waugh ◽  
J. R. Sommer
Keyword(s):  
Complex System ◽  
Electron Microscope ◽  
Sarcoplasmic Reticulum ◽  
Transmission Electron Microscope ◽  
Electron Microscopic ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Transmission Electron

Cardiac sarcoplasmic reticulum (SR) is a complex system of intracellular tubules that, due to their small size and juxtaposition to such electron-dense structures as mitochondria and myofibrils, are often inconspicuous in conventionally prepared electron microscopic material. This study reports a method with which the SR is selectively “stained” which facilitates visualizationwith the transmission electron microscope.

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