scholarly journals Activation by cholera toxin of adenylate cyclase solubilized from rat liver

1976 ◽  
Vol 157 (3) ◽  
pp. 785-787 ◽  
Author(s):  
S Van Heyningen
Keyword(s):  
Adenylate Cyclase ◽  
Cholera Toxin ◽  
Rat Liver ◽  
Thiol Group ◽  
Subunit B

Cholera toxin, or peptide A1 from the toxin, activates adenylate cyclase solubilized from rat liver with Lubrol PX, provided that cell sap, NAD+, ATP and thiol-group-containing compounds are present. The activation is abolished by antisera to whole toxin, but not to subunit B.

scholarly journals Short communications. Subunit A from cholera toxin is an activator of adenylate cyclase in pigeon erythrocytes

1975 ◽  
Vol 146 (1) ◽  
pp. 269-271 ◽  
Author(s):  
S Van Heyningen ◽  
C A King
Keyword(s):  
Adenylate Cyclase ◽  
Cholera Toxin ◽  
Cell Membranes ◽  
Erythrocyte Membranes ◽  
Subunit A ◽  
Subunit B

Intact cholera toxin and its purified subunit A both activate the adenylate cyclase of pigeon erythrocyte membranes, but subunit B does not. The activation by subunit A is unaffected by treatments that inhibit whole toxin by interfering with the binding of subunit B to cell membranes.

scholarly journals Studies on the time course and rate-limiting steps in the activation of adenylate cyclase in rat liver by cholera toxin

1978 ◽  
Vol 173 (1) ◽  
pp. 59-64 ◽  
Author(s):  
J Fischer ◽  
T R Kohler ◽  
L G Lipson ◽  
J Flores ◽  
P A Witkum ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Adenylate Cyclase ◽  
Cholera Toxin ◽  
Rat Liver ◽  
Time Course ◽  
Intact Cell ◽  
Intact Cells ◽  
Maximal Stimulation ◽  
Rate Limiting

Cholera toxin stimulates adenylate cyclase in rat liver after intravenous injection. The stimulation follows a short latent period of 10min, and maximum stimulation was attained at 120min. Half-maximal stimulation was achieved at 35min. In contrast with this lengthy time course in the intact cell, adenylate cyclase in broken-cell preparations of rat liver in vitro were maximally stimulated by cholera toxin (in the presence of NAD+) in 20min with half-maximal stimulation in 8min. Binding of cholera toxin to cell membranes by the B subunits is followed by translocation of the A subunit into the cell or cell membrane, and separation of the A1 polypeptide chain from the A2 chain by disulphide-bond reduction, and finally activation of adenylate cyclase by the A1 chain and NAD+. As the binding of cholera toxin is rapid, two possible rate-limiting steps could be the determinants of the long time course of action. These are translocation of the A1 chain from the outside of the cell membrane to its site of action (this includes the time required for separation from the whole toxin) or the availability of NAD+ for activation. When NAD+ concentrations in rat liver were elevated 4-fold, by the administration of nicotinamide, no change in the rate of activation of adenylate cyclase by cholera toxin was observed. Thus the intracellular concentration of NAD+ is not rate-limiting and the major rate-limiting determinant in intact cells must be between the time of toxin binding to the cell membrane and the appearance of subunit A1 at the enzyme site.

scholarly journals Requirement for guanosine triphosphate for cholera-toxin-catalysed incorporation of adenosine diphosphate ribose into rat liver plasma membranes and for activation of adenylate cyclase

1980 ◽  
Vol 186 (3) ◽  
pp. 749-754 ◽  
Author(s):  
C A Doberska ◽  
A J S MacPherson ◽  
B R Martin
Keyword(s):  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
Cholera Toxin ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Adenosine Diphosphate ◽  
Activation Process ◽  
Liver Plasma Membrane ◽  
Adp Ribosylation ◽  
A Subunit

1. Cholera toxin was shown to require the presence of GTP to activate rat liver plasma-membrane adenylate cyclase. ATP did not affect the activation process. 2. Cholera toxin catalysed the incorporation of 32P from NAD labelled in the alpha-phosphate group of the ADP moiety into a rat liver plasma-membrane protein with a subunit mol.wt. of 42 500. This is taken to demonstrate ADP-ribosylation. The ADP-ribosylation of this protein also required GTP and was unaffected by ATP. 3. Nicotinamide inhibited both the activation of adenylate cyclase by cholera toxin and the ADP-ribosylation of the protein of 42 500 subunit mol wt. Neither the activation nor the ADP-ribosylation could be reversed by treatment with nicotinamide in the presence of cholera toxin.

scholarly journals Activation of adenylate cyclase by cholera toxin in rat liver homogenates.

1976 ◽  
Vol 57 (2) ◽  
pp. 450-458 ◽  
Author(s):  
J Flores ◽  
P Witkum ◽  
G W Sharp
Keyword(s):  
Adenylate Cyclase ◽  
Cholera Toxin ◽  
Rat Liver ◽  
Liver Homogenates

scholarly journals Activity of covalently cross-linked cholera toxin with the adenylate cyclase of intact and lysed pigeon erythrocytes

1977 ◽  
Vol 168 (3) ◽  
pp. 457-463 ◽  
Author(s):  
S van Heyningen
Keyword(s):  
Cell Surface ◽  
Adenylate Cyclase ◽  
Cholera Toxin ◽  
Dimethyl Ester ◽  
Lag Phase ◽  
Ganglioside Gm1 ◽  
Whole Cells ◽  
Subunit B

Reaction of cholera toxin with NN'-bis(carboximidomethyl)tartaramide dimethyl ester produced several cross-linked species that had subunit B (which binds to the cell surface) and peptides A1 (which activates adenylate cyclase) and A2 all covalently joined together. This cross-linded material had activity with pigeon erythrocytes that was comparable in all respects with that of native toxin. It activated the adenylate cyclase of whole cells, showing a characteristic lag phase, and this activation was increased if the cells had been preincubated with ganglioside GM1, but abolished if the protein had been preincubated with the ganglioside. It activated the enzyme in lysed cells more strongly and without the lag phase. These results show that the toxin is active even when peptide A1 cannot be released from the rest of the molecule.

scholarly journals Cholera toxin requires oxidized nicotinamide-adenine dinucleotide to activate adenylate cyclase in purified rat liver plasma membranes

1977 ◽  
Vol 161 (3) ◽  
pp. 639-642 ◽  
Author(s):  
B R Martin ◽  
M D Houslay ◽  
E L Kennedy
Keyword(s):  
Adenylate Cyclase ◽  
Cholera Toxin ◽  
Rat Liver ◽  
Nicotinamide Adenine Dinucleotide ◽  
Plasma Membranes ◽  
Nicotinamide Adenine ◽  
Isolated Rat Liver ◽  
Liver Plasma Membranes ◽  
Rat Liver Plasma Membranes ◽  
Isolated Rat

Activation of adenylate cyclase in isolated rat liver plasma membranes by cholera toxin was demonstrated. The activation requires the presence of NAD+ and ATP and is irreversible.

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