scholarly journals Organization of thiol groups of electric-eel electric-organ sodium-plus-potassium ion-stimulated adenosine triphosphatase studied with bifunctional reagents

1980 ◽  
Vol 185 (3) ◽  
pp. 787-790 ◽  
Author(s):  
W E Harris ◽  
W L Stahl
Keyword(s):  
Adenosine Triphosphatase ◽  
Polar Solvent ◽  
Electric Organ ◽  
Thiol Group ◽  
Cross Linking ◽  
Thiol Groups ◽  
High Solubility ◽  
Efficient Inhibitor ◽  
Polar Environment ◽  
Electric Eel

The reactions of three bifunctional thiol-blocking reagents of differing cross-linking spans and two monofunctional thiol-blocking reagents with the Na+ + K+-stimulated ATPase of the electric-eel electric organ were examined. 1,5-Difluoro-2,4-dinitrobenzene with a cross-linking span of 0.3-0.5 nm (3-5 A) and high solubility in non-polar solvent was the most efficient inhibitor of enzyme activity; thus essential thiol groups exist in a non-polar environment and are approx. 0.3-0.5 nm (3-5 A) from their nearest thiol-group neighbours. Ligands promoting phosphorylation of the Na+ + K+-stimulated ATPase decreased the number of thiol groups bridged by 1,5-difluoro-2,4-dinitrobenzene and by 4,4'-difluoro-3,3'-dinitrodiphenyl sulphone [0.7-1.0 nm (7-10 A) span]. Phosphorylation is associated with a conformational change in the enzyme.

Chemorheology of Polysulfide Rubbers

1949 ◽  
Vol 22 (3) ◽  
pp. 712-730
Author(s):  
Marcos Mochulsky ◽  
Arthur V. Tobolsky
Keyword(s):  
Molecular Structure ◽  
Exchange Reaction ◽  
Thiol Group ◽  
Cross Linking ◽  
Thiol Groups ◽  
Disulfide Linkage ◽  
Cold Flow ◽  
Adjacent Chain ◽  
Chemical Type ◽  
Chemical Agents

Abstract Experimental results indicate that the socalled “cold flow” of polysulfide rubbers is almost certainly chemical rather than physical in nature. The term chemorheology has been adopted to describe this chemical type of plasticity. The experimental method employed in this investigation was the measurement of relaxation of stress in stretched rubber samples held at a constant elongation. The changes in relaxation rate produced by changing the molecular structure of the rubber (by cross-linking), by incorporating carbon black, by illuminating with ultraviolet light, and by treating the rubber with various chemical agents, such as sulfur, a thiol, and agents that destroy thiol groups, were studied by this method. From the results of the above experiments and from additional considerations, it is concluded that the chemical reaction responsible for cold flow is an intermolecular exchange reaction, and that this exchange reaction is probably an exchange between a terminal thiol group of one chain and a disulfide linkage of an adjacent chain.

scholarly journals The reactivity of the thiol groups of the adenosine triphosphatase of sarcoplasmic reticulum and their location on tryptic fragments of the molecule

1977 ◽  
Vol 167 (3) ◽  
pp. 739-748 ◽  
Author(s):  
David A. Thorley-Lawson ◽  
N. Michael Green
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Rate Constant ◽  
Adenosine Triphosphatase ◽  
Sodium Dodecyl ◽  
Thiol Group ◽  
Order Rate Constant ◽  
Reaction Rates ◽  
Cysteic Acid ◽  
Thiol Groups ◽  
Low Concentrations

The ATPase (adenosine triphosphatase) from sarcoplasmic reticulum contains 20 thiol groups/115000 daltons, measured by using either N-ethyl[14C]maleimide or 5,5′-dithiobis-(2-nitrobenzoate) in sodium dodecyl sulphate. After reduction there were 26 thiol groups, in good agreement with 26.5 residues of cysteic acid found by amino acid analysis. The difference between this and the 20 residues measured before reduction implies the presence of three disulphide residues. The same number of disulphide residues was found by direct measurement. Three to six fewer thiol groups were found in preparations made in the absence of dithiothreitol. The missing residues were accounted for as cysteic acid. The distribution of disulphide bonds and of exposed and buried thiol groups among the tryptic fragments of the molecule was measured after labelling with N-ethyl[14C]-maleimide. The disulphides were confined to fragment B (mol.wt. 55000), whereas several thiol groups were present on each of the fragments (A, B, A1 and A2). The kinetics of the reaction of the ATPase with 5,5′-dithiobis-(2-nitrobenzoate) showed that four or five of the thiol groups were unreactive in the absence of detergent and that 13 of the remainder reacted with a single first-order rate constant. In the presence of ATP and Ca2+ the reaction rate of all but two groups of this class was uniformly decreased. In the presence or absence of ATP and Ca2+ the rate constant for inactivation was close to the rate constant for this class, but was not identical with it. No selective protection of a specific active-site-thiol group was observed. Parallel experiments with sarcoplasmic reticulum gave similar results, except that the reaction rates were a little lower and there were two more buried groups. Solution of ATPase of sarcoplasmic reticulum in detergent greatly increased the reactivity of all thiol groups. The effects of low concentrations of deoxycholate were reversible. EGTA or low concentrations (0.02mm) of Ca2+ of Mg2+ had very little effect on the reactivity.

scholarly journals Phosphorylation states of the (Na+ + K+)-transporting ATPase in preparations from lamb kidney and electric-eel (Electophorus electricus) electric organ

1984 ◽  
Vol 218 (2) ◽  
pp. 341-345 ◽  
Author(s):  
W E Harris ◽  
W L Stahl
Keyword(s):  
Tertiary Structure ◽  
Electric Organ ◽  
State Level ◽  
Steady State Level ◽  
Thiol Groups ◽  
Phosphorylated Form ◽  
Kidney Enzyme ◽  
Electric Eel ◽  
The Difference ◽  
Stimulation Of

Phosphorylation states of the (Na+ + K+)-transporting ATPase were studied in highly purified preparations isolated from electric-eel electric organ and from lamb kidney. The steady-state level of phosphorylated lamb kidney enzyme, obtained by reaction with [gamma-32P]ATP, was not appreciably reduced in the presence of ADP unless oligomycin was present. The phosphorylated form of the electric-eel electric-organ enzyme was reduced by at least 95% under the same conditions, suggesting that the E1P state in the kidney enzyme is more transitory than that in electric organ. The level of phosphorylation from [32P]Pi was higher in the lamb kidney preparation than in the electric-organ preparation, and the difference in stimulation of phosphorylation by ouabain in the two preparations was striking. Ouabain increased the level of phosphorylation by 35% in the kidney preparation and 734% in the electric-organ preparation. The E2P state seems to be stabilized by ouabain in the latter preparation. These findings, as well as the different reactivities of the thiol groups to blocking reagents in these preparations, suggest that the tertiary structure in the enzyme isolated from these two sources is different.

scholarly journals Cross-linking experiments with the adenosine triphosphatase of sarcoplasmic reticulum

1979 ◽  
Vol 179 (1) ◽  
pp. 135-139 ◽  
Author(s):  
G M Hebdon ◽  
L W Cunningham ◽  
N M Green
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Adenosine Triphosphatase ◽  
Room Temperature ◽  
Cross Linking ◽  
Complete Oxidation ◽  
Thiol Groups ◽  
High Concentration ◽  
Disulphide Bonds ◽  
Dimethyl Suberimidate ◽  
Very High

The proteins of sarcoplasmic reticulum were cross-linked by rapid oxidation of thiol groups with I2. About two-thirds of the thiols were oxidized without any significant cross-linking, implying an extensive formation of intramolecular disulphide bonds. When the thiols were completely oxidized at room temperature a series of oligomers containing up to five molecules were observed, as well as large aggregates which were excluded from the gels. Complete oxidation at -10 degrees C left most of the ATPase (adenosine triphosphatase) as monomer. Similar results were obtained when copper-phenanthroline complexes or dimethyl suberimidate were used as cross-linking reagents. We conclude that most of the cross-linked species arise by linking of randomly colliding ATPase molecules which are present in the membrane at very high concentration.

scholarly journals The role of the thiol group in protein modification with methylglyoxal

2009 ◽  
Vol 74 (8-9) ◽  
pp. 867-883 ◽  
Author(s):  
Jelena Acimovic ◽  
Bojana Stanimirovic ◽  
Ljuba Mandic
Keyword(s):  
Protein Modification ◽  
Time Course ◽  
Thiol Group ◽  
Model Systems ◽  
Cross Linking ◽  
Thiol Groups ◽  
Serum Albumins ◽  
Stable Product ◽  
Protein Cross Linking

Methylglyoxal is a highly reactive ?-oxoaldehyde with elevated production in hyperglycemia. It reacts with nucleophilic Lys and Arg side-chains and N-terminal amino groups causing protein modification. In the present study, the importance of the reaction of the Cys thiol group with methylglyoxal in protein modification, the competitiveness of this reaction with those of amino and guanidine groups, the time course of these reactions and their role and contribution to protein cross-linking were investigated. Human and bovine serum albumins were used as model systems. It was found that despite the very low levels of thiol groups on the surface of the examined protein molecules (approx. 80 times lower than those of amino and guanidino groups), a very high percentage of it reacts (25-85 %). The amount of reacted thiol groups and the rate of the reaction, the time for the reaction to reach equilibrium, the formation of a stable product and the contribution of thiol groups to protein cross-linking depend on the methylglyoxal concentration. The product formed in the reaction of thiol and an insufficient quantity of methylglyoxal (compared to the concentrations of the groups accessible for modification) participates to a significant extent (4 %) to protein cross-linking. Metformin applied in equimolar concentration with methylglyoxal prevents its reaction with amino and guanidino groups but, however, not with thiol groups.

scholarly journals 13C-n.m.r. of the cyanylated β-lactoglobulins: evidence that Cys-121 provides the thiol group of β-lactoglobulins A and B

1994 ◽  
Vol 302 (2) ◽  
pp. 511-516 ◽  
Author(s):  
P Phelan ◽  
J P Malthouse
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Thiol Group ◽  
Equimolar Mixture ◽  
Thiol Groups ◽  
Exchange Reactions ◽  
Polar Environment ◽  
Alkaline Denaturation ◽  
The One

The thiol groups of beta-lactoglobulins A and B have been cyanylated using [13C]KCN. The samples of [cyanato-13C]-cyanylated-beta-lactoglobulins A and B which we prepared had signals at 109.7 p.p.m. and 114.4 p.p.m. We conclude that the thiocyanate carbon having a chemical shift of 109.7 p.p.m. is in an apolar environment similar to a cyclohexane solvent, whereas the thiocyanate carbon having a chemical shift of 114.4 p.p.m. is in a polar environment similar to water. The signals with chemical shifts of 109.7 p.p.m. are assigned to the thiocyanate carbons of the native [cyanato-13C]cyanylated-beta-lactoglobulins A and B. We deduce that the signal at 114.4 p.p.m. is due to an irreversibly denatured/unfolded species produced by alkaline denaturation, which is caused by intramolecular thiol/disulphide exchange occurring during our cyanylation procedure. We propose that Cys-119 is cyanylated in the irreversibly denatured species and Cys-121 is cyanylated in the native [cyanato-13C]cyanylated-beta-lactoglobulins A and B. We suggest that the same intramolecular thiol-disulphide exchange reactions occurred when McKenzie and co-workers [McKenzie, Ralston and Shaw (1972) Biochemistry 11, 4539-4547] alkylated beta-lactoglobulins with iodoacetamide. Therefore the one mol of thiol/mol of monomer in the native beta-lactoglobulins is due to the thiol of Cys-121 and is not due to an equimolar mixture of Cys-119 and Cys-121 as they suggested.

scholarly journals The third form electric organ discharge of electric eels

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jun Xu ◽  
Xiang Cui ◽  
Huiyuan Zhang
Keyword(s):  
High Voltage ◽  
Low Voltage ◽  
Electric Organ Discharge ◽  
Electric Organ ◽  
The Third ◽  
Electric Organs ◽  
Electric Eel ◽  
New Finding ◽  
Discharge Behavior ◽  
Unique Species

AbstractThe electric eel is a unique species that has evolved three electric organs. Since the 1950s, electric eels have generally been assumed to use these three organs to generate two forms of electric organ discharge (EOD): high-voltage EOD for predation and defense and low-voltage EOD for electrolocation and communication. However, why electric eels evolved three electric organs to generate two forms of EOD and how these three organs work together to generate these two forms of EOD have not been clear until now. Here, we present the third form of independent EOD of electric eels: middle-voltage EOD. We suggest that every form of EOD is generated by one electric organ independently and reveal the typical discharge order of the three electric organs. We also discuss hybrid EODs, which are combinations of these three independent EODs. This new finding indicates that the electric eel discharge behavior and physiology and the evolutionary purpose of the three electric organs are more complex than previously assumed. The purpose of the middle-voltage EOD still requires clarification.

scholarly journals Half-sites oxidation of bovine liver uridine diphosphate glucose dehydrogenase

1978 ◽  
Vol 173 (2) ◽  
pp. 701-704 ◽  
Author(s):  
J S Franzen ◽  
P Marchetti ◽  
R Ishman ◽  
J Ashcom
Keyword(s):  
Catalytic Activity ◽  
Glucose Dehydrogenase ◽  
Bovine Liver ◽  
Thiol Group ◽  
Catalytic Site ◽  
Uridine Diphosphate ◽  
Thiol Groups ◽  
Irreversible Denaturation ◽  
Diphosphate Glucose ◽  
Uridine Diphosphate Glucose Dehydrogenase

6,6-Dithiodinicotinate shows half-of-the-sites reactivity towards the six catalytic-site thiol groups of bovine liver UDP-glucose dehydrogenase. The reagent introduces three intrasubunit disulphide linkages between catalytic-site thiol groups and non-catalytic-site thiol groups and abrogates 60% of the catalytic activity of the hexameric enzyme; excess 2-mercaptoethanol rapidly restores full catalytic activity. These results show the half-of-the-sites behaviour of the enzyme with the reagent and the presence of a non-catalytic-site thiol group capable of forming a disulphide linkage with a catalytic-site thiol group on the same subunit without irreversible denaturation.

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