Monoclonal antibodies to the Ca2+ + Mg2+-dependent ATPase of sarcoplasmic reticulum identify polymorphic forms of the enzyme and indicate the presence in the enzyme of a classical high-affinity Ca2+ binding site

1984 ◽  
Vol 16 (5-6) ◽  
pp. 441-464 ◽  
Author(s):  
Elizabeth Zubrzycka-Gaarn ◽  
Glen MacDonald ◽  
Laurie Phillips ◽  
Annelise O. Jorgensen ◽  
David H. MacLennan
Keyword(s):  
Monoclonal Antibodies ◽  
Sarcoplasmic Reticulum ◽  
Binding Site ◽  
High Affinity ◽  
Dependent Atpase ◽  
Polymorphic Forms

scholarly journals Interactions of a Reversible Ryanoid (21-Amino-9α-Hydroxy-Ryanodine) with Single Sheep Cardiac Ryanodine Receptor Channels

1998 ◽  
Vol 112 (1) ◽  
pp. 55-69 ◽  
Author(s):  
Bhavna Tanna ◽  
William Welch ◽  
Luc Ruest ◽  
John L. Sutko ◽  
Alan J. Williams
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Binding Site ◽  
Single Channel ◽  
Single Channels ◽  
Open Probability ◽  
Release Channel ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Channel Protein ◽  
High Affinity ◽  
Conductance State

The binding of ryanodine to a high affinity site on the sarcoplasmic reticulum Ca2+-release channel results in a dramatic alteration in both gating and ion handling; the channel enters a high open probability, reduced-conductance state. Once bound, ryanodine does not dissociate from its site within the time frame of a single channel experiment. In this report, we describe the interactions of a synthetic ryanoid, 21-amino-9α-hydroxy-ryanodine, with the high affinity ryanodine binding site on the sheep cardiac sarcoplasmic reticulum Ca2+-release channel. The interaction of 21-amino-9α-hydroxy-ryanodine with the channel induces the occurrence of a characteristic high open probability, reduced-conductance state; however, in contrast to ryanodine, the interaction of this ryanoid with the channel is reversible under steady state conditions, with dwell times in the modified state lasting seconds. By monitoring the reversible interaction of this ryanoid with single channels under voltage clamp conditions, we have established a number of novel features of the ryanoid binding reaction. (a) Modification of channel function occurs when a single molecule of ryanoid binds to the channel protein. (b) The ryanoid has access to its binding site only from the cytosolic side of the channel and the site is available only when the channel is open. (c) The interaction of 21-amino-9α-hydroxy-ryanodine with its binding site is influenced strongly by transmembrane voltage. We suggest that this voltage dependence is derived from a voltage-driven conformational alteration of the channel protein that changes the affinity of the binding site, rather than the translocation of the ryanoid into the voltage drop across the channel.

scholarly journals A kinetic model for Ca2+ efflux mediated by the Ca2+ + Mg2+-activated ATPase of sarcoplasmic reticulum

1987 ◽  
Vol 245 (3) ◽  
pp. 713-721 ◽  
Author(s):  
J M McWhirter ◽  
G W Gould ◽  
J M East ◽  
A G Lee
Keyword(s):  
Experimental Data ◽  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Kinetic Model ◽  
Atpase Activity ◽  
Binding Site ◽  
Binding Sites ◽  
Adenine Nucleotides ◽  
Contraction Coupling ◽  
High Affinity

We present a model for Ca2+ efflux from vesicles of sarcoplasmic reticulum (SR). It is proposed that efflux is mediated by the Ca2+ + Mg2+-activated ATPase that is responsible for Ca2+ uptake in this system. In the normal ATPase cycle of the ATPase, phosphorylation of the ATPase is followed by a conformational change in which the Ca2+-binding sites change from being outward-facing and of high affinity to being inward-facing and of low affinity. To mediate Ca2+ efflux, it is proposed that the ATPase can adopt a conformation in which the Ca2+-binding sites are of low affinity but still outward-facing. It is shown that experimental data on the rates of Ca2+ efflux can be simulated in terms of this model, with Ca2+-binding-site affinities previously proposed to explain ATPase activity [Gould, East, Froud, McWhirter, Stefanova & Lee (1986) Biochem. J. 237, 217-227]. Effects of Mg2+ and adenine nucleotides on efflux rates are explained. It is suggested that Ca2+ efflux from SR mediated by the ATPase could be important in excitation-contraction coupling in skeletal muscle.

scholarly journals High-affinity Ca2+ -binding site inhibiting Ca2+ release from sarcoplasmic reticulum

FEBS Letters ◽  
1989 ◽  
Vol 243 (1) ◽  
pp. 88-92 ◽  
Author(s):  
Anat Argaman ◽  
Varda Shoshan-Barmatz
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Binding Site ◽  
High Affinity

Conformation as the Therapeutic Target for Neurodegenerative Diseases

2017 ◽  
Vol 14 (4) ◽  
pp. 393-402 ◽  
Author(s):  
Rajaraman Krishnan ◽  
Franz Hefti ◽  
Haim Tsubery ◽  
Michal Lulu ◽  
Ming Proschitsky ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Neurodegenerative Diseases ◽  
Protein Misfolding ◽  
Specific Binding ◽  
Drug Candidate ◽  
High Affinity ◽  
Novel Approach ◽  
Multiple Protein ◽  
Clinical Benefits ◽  
Effective Drugs

Therapeutic strategies that target pathways of protein misfolding and the toxicity of intermediates along these pathways are mainly at discovery and early development stages, with the exception of monoclonal antibodies that have mainly failed to produce convincing clinical benefits in late stage trials. The clinical failures represent potentially critical lessons for future neurodegenerative disease drug development. More effective drugs may be achieved by pursuing the following two strategies. First, conformational targeting of aggregates of misfolded proteins, rather than less specific binding that includes monomer subunits, which vastly outnumber the toxic targets. Second, since neurodegenerative diseases frequently include more than one potential protein pathology, generic targeting of aggregates by shape might also be a crucial feature of a drug candidate. Incorporating both of these critical features into a viable drug candidate along with high affinity binding has not been achieved with small molecule approaches or with antibody fragments. Monoclonal antibodies developed so far are not broadly acting through conformational recognition. Using GAIM (General Amyloid Interaction Motif) represents a novel approach that incorporates high affinity conformational recognition for multiple protein assemblies, as well as recognition of an array of assemblies along the misfolding pathway between oligomers and fibers. A GAIM-Ig fusion, NPT088, is nearing clinical testing.

Sign in / Sign up

Export Citation Format

Share Document