scholarly journals The random-coil ‘C’ fragment of the dihydropyridine receptor II-III loop can activate or inhibit native skeletal ryanodine receptors

2003 ◽  
Vol 372 (2) ◽  
pp. 305-316 ◽  
Author(s):  
Claudia S. HAARMANN ◽  
Daniel GREEN ◽  
Marco G. CASAROTTO ◽  
Derek R. LAVER ◽  
Angela F. DULHUNTY
Keyword(s):  
Lipid Bilayers ◽  
Rate Constant ◽  
Ryanodine Receptors ◽  
Dihydropyridine Receptor ◽  
Random Coil ◽  
Dynamic Changes ◽  
Independent Manner ◽  
Loop Sequence ◽  
Coil Structure ◽  
Random Coil Structure

The actions of peptide C, corresponding to 724Glu–Pro760 of the II–III loop of the skeletal dihydropyridine receptor, on ryanodine receptor (RyR) channels incorporated into lipid bilayers with the native sarcoplasmic reticulum membrane show that the peptide is a high-affinity activator of native skeletal RyRs at cytoplasmic concentrations of 100 nM–10 μM. In addition, we found that peptide C inhibits RyRs in a voltage-independent manner when added for longer times or at higher concentrations (up to 150 μM). Peptide C had a random-coil structure indicating that it briefly assumes a variety of structures, some of which might activate and others which might inhibit RyRs. The results suggest that RyR activation and inhibition by peptide C arise from independent stochastic processes. A rate constant of 7.5×105 s−1·M−1 was obtained for activation and a lower estimate for the rate constant for inhibition of 5.9×103 s−1·M−1. The combined actions of peptide C and peptide A (II–III loop sequence 671Thr–Leu690) showed that peptide C prevented activation but not blockage of RyRs by peptide A. We suggest that the effects of peptide C indicate functional interactions between a part of the dihydropyridine receptor and the RyR. These interactions could reflect either dynamic changes that occur during excitation–contraction coupling or interactions between the proteins at rest.

scholarly journals Imperatoxin A Induces Subconductance States in Ca2+ Release Channels (Ryanodine Receptors) of Cardiac and Skeletal Muscle

1998 ◽  
Vol 111 (5) ◽  
pp. 679-690 ◽  
Author(s):  
Ashutosh Tripathy ◽  
Wolfgang Resch ◽  
Le Xu ◽  
Hector H. Valdivia ◽  
Gerhard Meissner
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Binding Site ◽  
Lipid Bilayers ◽  
Rate Constant ◽  
Single Channel ◽  
Voltage Drop ◽  
Ryanodine Receptors ◽  
Subconductance States ◽  
Single Channel Currents

Single-channel and [3H]ryanodine binding experiments were carried out to examine the effects of imperatoxin activator (IpTxa), a 33 amino acid peptide isolated from the venom of the African scorpion Pandinus imperator, on rabbit skeletal and canine cardiac muscle Ca2+ release channels (CRCs). Single channel currents from purified CRCs incorporated into planar lipid bilayers were recorded in 250 mM KCl media. Addition of IpTxa in nanomolar concentration to the cytosolic (cis) side, but not to the lumenal (trans) side, induced substates in both ryanodine receptor isoforms. The substates displayed a slightly rectifying current–voltage relationship. The chord conductance at −40 mV was ∼43% of the full conductance, whereas it was ∼28% at a holding potential of +40 mV. The substate formation by IpTxa was voltage and concentration dependent. Analysis of voltage and concentration dependence and kinetics of substate formation suggested that IpTxa reversibly binds to the CRC at a single site in the voltage drop across the channel. The rate constant for IpTxa binding to the skeletal muscle CRC increased e-fold per +53 mV and the rate constant of dissociation decreased e-fold per +25 mV applied holding potential. The effective valence of the reaction leading to the substate was ∼1.5. The IpTxa binding site was calculated to be located at ∼23% of the voltage drop from the cytosolic side. IpTxa induced substates in the ryanodine-modified skeletal CRC and increased or reduced [3H]ryanodine binding to sarcoplasmic reticulum vesicles depending on the level of channel activation. These results suggest that IpTxa induces subconductance states in skeletal and cardiac muscle Ca2+ release channels by binding to a single, cytosolically accessible site different from the ryanodine binding site.

scholarly journals Structure and dynamics of the RNAPII CTDsome with Rtt103

2017 ◽  
Vol 114 (42) ◽  
pp. 11133-11138 ◽  
Author(s):  
Olga Jasnovidova ◽  
Tomas Klumpler ◽  
Karel Kubicek ◽  
Sergei Kalynych ◽  
Pavel Plevka ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Coiled Coil ◽  
Random Coil ◽  
Sequence Complexity ◽  
Structure And Dynamics ◽  
Coiled Coil Domain ◽  
Transcription Termination Factor ◽  
Coil Structure ◽  
Random Coil Structure ◽  
Long Rod

RNA polymerase II contains a long C-terminal domain (CTD) that regulates interactions at the site of transcription. The CTD architecture remains poorly understood due to its low sequence complexity, dynamic phosphorylation patterns, and structural variability. We used integrative structural biology to visualize the architecture of the CTD in complex with Rtt103, a 3′-end RNA-processing and transcription termination factor. Rtt103 forms homodimers via its long coiled-coil domain and associates densely on the repetitive sequence of the phosphorylated CTD via its N-terminal CTD-interacting domain. The CTD–Rtt103 association opens the compact random coil structure of the CTD, leading to a beads-on-a-string topology in which the long rod-shaped Rtt103 dimers define the topological and mobility restraints of the entire assembly. These findings underpin the importance of the structural plasticity of the CTD, which is templated by a particular set of CTD-binding proteins.

N.M.R. studies on myelin basic protein. I. 13C spectra in aqueous solutions

1978 ◽  
Vol 31 (11) ◽  
pp. 2367 ◽  
Author(s):  
BE Chapman ◽  
WJ Moore
Keyword(s):  
Myelin Basic Protein ◽  
Basic Protein ◽  
Polypeptide Chain ◽  
Random Coil ◽  
Side Chain ◽  
Amino Acid Residues ◽  
Native Protein ◽  
Denatured Protein ◽  
Coil Structure ◽  
Random Coil Structure

Carbon-13 n.m.r, spectra have been obtained for bovine myelin basic protein at pD 4.4 in D2O and in 6 M guanidine deuterochloride solutions. Chemical-shift differences between resonances from some amino acid residues are interpreted in terms of structured regions in the polypeptide chain of the native protein, whereas the denatured protein displays the spectrum expected for an essentially random coil. Measurements of T1 and n.O.e. provide quantitative data on the dynamics of the backbone and side-chain carbons, and give support to the conclusion that the native protein does not have a random-coil structure.

scholarly journals Microwave Pretreatment and Enzymolysis Optimization of the Lotus Seed Protein

2019 ◽  
Vol 6 (2) ◽  
pp. 28
Author(s):  
Bi Gohi ◽  
Jinze Du ◽  
Hong-Yan Zeng ◽  
Xiao-ju Cao ◽  
Kai Zou
Keyword(s):  
Secondary Structure ◽  
Seed Protein ◽  
Random Coil ◽  
Degree Of Hydrolysis ◽  
High Power Microwave ◽  
Lotus Seed ◽  
Coil Structure ◽  
Random Coil Structure ◽  
Optimized Conditions ◽  
Power Microwave

Pretreatment with a microwave was conducted before enzymolysis and shown to enhance the enzymolysis, which changed the secondary structure of the lotus seed protein. Under high-power microwave irradiation, sub bonds of the protein were broken, causing disaggregation and unfolding of the secondary structure, namely a decrease in the intermolecular aggregate structure and increase in the random coil structure, making the protein bonds susceptible to papain in the enzymolysis. On the other hand, a response surface methodology (RSM) was launched to investigate the influence of the enzymolysis process variables on the DH (degree of hydrolysis). The statistical analysis revealed that the optimized conditions were a protein substrate concentration of 15 g/L, pH of 5.5, enzymolysis temperature of 57 °C, papain amount of 0.5 g/L, and enzymolysis time of 45 min, for which the predicted value of the DH was 35.64%. The results indicated that a microwave also had better potential for applications in the enzymolysis of foods.

Photoluminescence dynamics of copper nanoclusters synthesized by cellulase: role of the random-coil structure

RSC Advances ◽  
2016 ◽  
Vol 6 (60) ◽  
pp. 55539-55545 ◽  
Author(s):  
Akanksha Singh ◽  
Tripti Rai ◽  
Debashis Panda
Keyword(s):  
Green Emission ◽  
Luminescent Properties ◽  
Random Coil ◽  
Copper Nanoclusters ◽  
Coil Structure ◽  
Random Coil Structure ◽  
Directed Synthesis

Cellulase-directed synthesis of magic numbered Cu NCs with blue-, cyan-, and green emission from Cu12, Cu20, and Cu34, respectively is presented. The random coil structure of enzyme dictates the size and luminescent properties of Cu NCs.

scholarly journals Regulation of skeletal ryanodine receptors by dihydropyridine receptor II–III loop C-region peptides: relief of Mg2+ inhibition

2005 ◽  
Vol 387 (2) ◽  
pp. 429-436 ◽  
Author(s):  
Claudia S. HAARMANN ◽  
Angela F. DULHUNTY ◽  
Derek R. LAVER
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Lipid Bilayers ◽  
Surface Membrane ◽  
Ryanodine Receptors ◽  
Dihydropyridine Receptor ◽  
Physical Interaction ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
High Affinity ◽  
Ca2 Channels

The aim of the present study was to explore interactions between surface-membrane DHPR (dihydropyridine receptor) Ca2+ channels and RyR (ryanodine receptor) Ca2+ channels in skeletal-muscle sarcoplasmic reticulum. The C region (725Phe-Pro742) of the linker between the 2nd and 3rd repeats (II–III loop) of the α1 subunit of skeletal DHPRs is essential for skeletal excitation–contraction coupling, which requires a physical interaction between the DHPR and RyR and is independent of external Ca2+. Little is known about the regulatory processes that might take place when the two Ca2+ channels interact. Indeed, interactions between C fragments of the DHPR (C peptides) and RyR have different reported effects on Ca2+ release from the sarcoplasmic reticulum and on RyR channels in lipid bilayers. To gain insight into functional interactions between the proteins and to explore different reported effects, we examined the actions of C peptides on RyR1 channels in lipid bilayers with three key RyR regulators, Ca2+, Mg2+ and ATP. We identified four discrete actions: two novel, low-affinity (>10 μM), rapidly reversible effects (fast inhibition and decreased sensitivity to Mg2+ inhibition) and two slowly reversible effects (high-affinity activation and a slow-onset, low-affinity inhibition). Fast inhibition and high-affinity activation were decreased by ATP. Therefore peptide activation in the presence of ATP and Mg2+, used with Ca2+ release assays, depends on a mechanism different from that seen when Ca2+ is the sole agonist. The relief of Mg2+ inhibition was particularly important since RyR activation during excitation–contraction coupling depends on a similar decrease in Mg2+ inhibition.

scholarly journals The glycine locating at random coil of picornaviruses VP3 enhances viral pathogenicity by targeting p53 to promote apoptosis and autophagy

2019 ◽  
Author(s):  
Ruoqing Mao ◽  
Fan Yang ◽  
Dehui Sun ◽  
Xiaoli Zhou ◽  
Zixiang Zhu ◽  
...  
Keyword(s):  
Enterovirus 71 ◽  
Foot And Mouth Disease ◽  
Underlying Mechanism ◽  
Skin Lesions ◽  
Random Coil ◽  
Autophagy Induction ◽  
Coil Structure ◽  
Mouth Disease Virus ◽  
Random Coil Structure ◽  
Seneca Valley Virus

AbstractPicornaviruses, comprising important and widespread pathogens of humans and animals, have evolved to control apoptosis and autophagy for their replication and spread. However, the underlying mechanism of the association between apoptosis/autophage and viral pathogenicity remains unclear. In the present study, VP3 of picornaviruses was demonstrated to induce apoptosis and autophagy. Foot-and-mouth disease virus (FMDV), which served as a research model here, can strongly induce both apoptosis and autophagy in the skin lesions. By directly interacting with p53, FMDV-VP3 facilitates its phosphorylation and translocation, resulting in Bcl-2 family-mediated apoptosis and LC3-dependent autophagy. The single residue Gly129 of FMDV-VP3 plays a crucial role in apoptosis and autophagy induction and the interaction with p53. Consistently, the comparison of rescued FMDV with mutated Gly129 and parental virus showed that the Gly129 is indispensable for viral replication and pathogenicity. More importantly, the Gly129 locates at a bend region of random coil structure, the mutation of Gly to Ala remarkably shrunk the volume of viral cavity. Coincidentally, the Gly is conserved in the similarly location of other picornaviruses, including poliovirus (PV), enterovirus 71 (EV71), coxsackievirus (CV) and seneca valley virus (SVA). This study demonstrates that picornaviruses induce apoptosis and autophagy to facilitate its pathogenicity and the Gly is functional site, providing novel insights into picornavirus biology.

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