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Alterations in detergent solubility of heterotrimeric G proteins after chronic activation of G(i/o)-coupled receptors: changes in detergent solubility are in correlation with onset of adenylyl cyclase superactivation.

Prolonged G(i/o) protein-coupled receptor activation has been shown to lead to receptor internalization and receptor desensitization. In addition, it is well established that although acute activation of these receptors leads to inhibition of adenylyl cyclase (AC), long-term activation results in increased AC activity (especially evident on removal of the inhibitory agonist), a phenomenon defined as AC superactivation or sensitization. Herein, we show that chronic exposure to agonists of G(i)-coupled receptors also leads to a decrease in cholate detergent solubility of G protein subunits, and that antagonist treatment after such chronic agonist exposure leads to a time-dependent reversal of the cholate insolubility. With Chinese hamster ovary and COS cells transfected with several G(i/o)-coupled receptors (i.e., mu- and kappa-opioid, and m(4)-muscarinic), we observed that although no overall change occurred in total content of G(alphai)- and beta(1)-subunits, chronic agonist treatment led to a marked reduction in the ability of 1% cholate to solubilize G(betagamma) as well as G(alphai). This solubility shift is exclusively observed with G(alphai), and was not seen with G(alphas). The disappearance and reappearance of G(alphai) and G(betagamma) subunits from and to the detergent-soluble fractions occur with similar time courses as observed for the onset and disappearance of AC superactivation. Lastly, pertussis toxin, which blocks acute and chronic agonist-induced AC inhibition and superactivation, also blocks the shift in detergent solubility. These results suggest a correlation between the solubility shift of the heterotrimeric G(i) protein and the generation of AC superactivation.

Adenylate Cyclase Toxin↗

A detergent-activated tyrosinase from Xenopus laevis. II. Detergent activation and binding.

Tyrosinase purified from Xenopus is enzymatically inactive in aqueous buffers but is activated for both of its substrates by exposure to a variety of anionic detergents. Cationic and nonionic detergents, as well as a variety of other agents are ineffective. This stimulation by detergents is observed at all stages of the purification (Wittenberg, C., and Triplett, E. L. (1985) J. Biol. Chem. 260, 12535-12541). Sodium dodecyl sulfate (NaDodSO4) is the most effective activator, and it was chosen for further characterization. Activation of both activities by NaDodSO4 is rapid and concentration dependent, resulting in maximal activity after 4 min at 1 mM NaDodSO4. NaDodSO4 treatment also results in both long and short term stabilization of the enzyme. The activation and stabilization are separable but stoichiometrically related. Both effects occur well below the critical micelle concentration suggesting that the interaction of NaDodSO4 monomers with the enzyme is involved in these processes. In support of this suggestion, the enzyme is shown to bind NaDodSO4 with high affinity, as determined by equilibrium dialysis. The isotherm for this binding correlates well with the requirement of NaDodSO4 for both activation and stabilization. All three effects are observable at 3 X 10(-5) M NaDodSO4 in the presence of 0.1 M sodium chloride. Activation and stabilization are maximal at 6 X 10(-4) M NaDodSO4, the critical micelle concentration of NaDodSO4 under these conditions.

Animals↗

A viral coat glycoprotein (gp52MuMTV) has detergent-sensitive and detergent-resistant epitopes in the same molecule.

Two monoclonal antibodies (IIB5 and IC12) specific for the gp52 coat glycoprotein of mouse mammary tumor virus are directed against epitopes on the gp52 that are sensitive to a non-ionic detergent, Nonidet P-40. There are other epitopes on this molecule that are stable in the detergent, as seen in immunoprecipitation studies with other anti-gp52 monoclonal antibodies (VE7, IIIA1, IVC11).

Antibodies, Monoclonal↗

Removal of detergent and solvent from solvent-detergent-treated immunoglobulins.

The solvent-detergent (S/D) method was applied for inactivation of lipid-enveloped viruses during the production of immunoglobulins. Amberlite XAD-7 resin was used for removal of solvent (tri-n-butyl phosphate, TnBP) and detergent (Triton X-100) after the performed S/D inactivation procedure. The S/D reagents from the immunoglobulin preparation were adsorbed on Amberlite XAD-7, while immunoglobulins passed through the column and retained their biological activity. Using the method developed here, the final immunoglobulin preparation contains less than 1 ppm of Triton X-100 and less than 2 ppm TnBP.

Acrylic Resins↗

Eight gram-negative bacteria are 10,000 times more sensitive to cationic detergents than to anionic detergents.

In liquid culture, eight typical gram-negative bacteria were ca. 10,000-fold more sensitive to cationic detergents than to the anionic detergent sodium dodecyl sulfate. Cetyltrimethylammonium bromide (CTAB) was inhibitory at concentrations ranging from 0.0006% to 0.01%. Four pseudomonads able to form biofilms were ca. 1000-fold more resistant to CTAB on Luria-Bertani agar plates than they were in liquid culture. A lasI mutant of Pseudomonas aeruginosa was only able to tolerate 0.1% CTAB on Luria-Bertani agar plates but could tolerate 5% CTAB when supplemented with homoserine lactone containing culture supernatants.

4-Butyrolactone↗

Substitution of neutral detergent fiber from forage with neutral detergent fiber from by-products in the diets of lactating cows.

Four lactating dairy cows that were ruminally and duodenally cannulated were used in an experiment with a 4 x 4 Latin square design to determine the effects of the substitution of neutral detergent fiber (NDF) from forage with NDF from wheat middlings, corn gluten feed, or a blend of distillers dried grains and hominy. Dietary crude protein and NDF averaged 18 and 31%, respectively, for the diet with 71.2% of the NDF from forage (control diet) and for diets with 55% of the NDF from forage (by-product diets). The substitution of NDF from these by-products for forage NDF did not affect dry matter intake (20.1 kg/d) or digestibility of organic matter. Total tract digestibility of acid detergent fiber was lower for cows fed the diet containing a blend of distillers dried grains and hominy than for cows fed the diet containing corn gluten feed. Microbial crude protein synthesis, milk production (23.9 kg/d), and milk fat percentage were similar for all cows, regardless of diet. Cows fed the diets containing wheat middlings or a blend of distillers dried grains and hominy had reduced ruminal pH compared with that of cows fed the diet containing corn gluten feed or the control diet. Diets containing 55% of total NDF from forage with 31% of total NDF from corn gluten feed, wheat middlings, or a blend of distillers dried grains and hominy can supply sufficient effective fiber to maintain normal ruminal function.

Ammonia↗

Denaturation and renaturation of bacteriorhodopsin in detergents and lipid-detergent mixtures.

The denatured and renatured states of bacteriorhodopsin have been studied in detergents and lipid/detergent mixtures by using ultraviolet and visible light absorption spectroscopy, fluorescence spectroscopy, and circular dichroism. Upon solubilization in sodium dodecyl sulfate, bacteriorhodopsin undergoes denaturation with partial loss of the secondary structure and loss of retinal binding ability. In contrast, delipidated bacteriorhodopsin retains its native structure in deoxycholate and undergoes denaturation only on photobleaching, which results in a partial loss of the secondary structure. Native secondary structure spontaneously reforms upon addition of phospholipid/cholate mixtures to bacterio-opsin denatured in sodium dodecyl sulfate. Upon subsequent addition of retinal, up to 95% of the native chromophore (lambdamax = 550-560 nm) is restored. Renaturation also restores the characteristics of light and dark adaptation and tight retinal binding (Kb greater than 10(7) M-1). Renaturation of delipidated bacteriorhodopsin denatured in sodium dodecyl sulfate also occurs without phospholipid upon the addition of retinal and Triton X-100 or octyl glucoside. The equilibrium between monomeric and oligomeric states of bacteriorhodopsin has been studied by circular dichroism and fluorescence quenching. Bacteriorhodopsin renatured with Triton X-100 or phospholipid/cholate is monomeric. However, removal of the detergents from renatured protein under specific conditions results in formation of an oligomer in which quaternary interactions are regenerated. The application of fluorescence quenching to the determination of oligomeric size in intrinsic membrane proteins is discussed.

Bacteriorhodopsins↗

Proteolytic detergent enzymes enhance the allergic antibody responses of guinea pigs to nonproteolytic detergent enzymes in a mixture: implications for occupational exposure.

A guinea pig intratracheal test was developed to assess the respiratory allergenicity of enzymes used in the detergent industry. Information gained from this test was used in a process for setting operational exposure guidelines to protect worker health. Mixtures of enzyme proteins were given to guinea pigs once per week for 10 weeks to determine whether there were interactions among enzymes that affected the induction of antibody responses to each enzyme in the mixture. Passive cutaneous anaphylaxis antibody titers against each enzyme were measured in sera. Mixtures of two or three enzymes always consisted of a protease (Alcalase, Savinase; Novo Industri A/S) with an alpha-amylase (Termamyl; Novo Industri A/S), a lipase (Lipolase; Novo Industri A/S), or both. Control animals were exposed to single enzymes. The antibody titers to Termamyl and Lipolase were significantly greater in animals dosed with the protease-containing mixtures as compared with control animals dosed with a single enzyme. Antibody titers to the protease were unchanged in the presence of additional enzymes in the mixture. Complete inactivation of protease activity abrogated the enhanced antibody response to Lipolase. Inhalation exposure of guinea pigs to a mixture of Alcalase and Lipolase also resulted in higher antibody titers to Lipolase as compared with animals exposed by inhalation to Lipolase alone, showing that the enhanced response was not due to intratracheal delivery of antigen to the respiratory tract. These results show that proteolytic enzymes in a mixture enhance antibody responses to other enzymes. This should be considered when defining exposure guidelines for protease-containing enzyme mixtures.

Administration, Inhalation↗

Enzyme exposure, smoking and lung function in employees in the detergent industry over 20 years. Medical Subcommittee of the UK Soap and Detergent Industry Association.

This study was undertaken to examine the long term relationship between lung function, smoking and exposure to enzymes in the detergent industry. A total of 731 male workers from five locations in the United Kingdom were subject to respiratory health surveillance including lung function testing over a period of 4-20 years. Exposure groups were defined by job history. Significantly different rates of fall in FEV1 and FVC with time were found by geographical location and by smoking habit, but there were no consistent trends with enzyme exposure.

Adult↗

Properties of purified detergent-resistant phospholipase A of Escherichia coli K-12. Inactivation, and protection with detergents and phospholipids.

A crude preparation of membrane-bound phospholipase A (detergent-resistant) in Escherichia coli K-12 cells was found to be quite stable or even apparently activated on incubation at 100 degrees C, but became strikingly thermolabile when it was highly purified and Triton X-100 was removed from the purified enzyme preparation. The rate of inactivation showed a biphasic temperature dependence: inactivation was rapid at 37 degrees C and also above 70 degrees C. Inactivation above 70 degrees C changed the mobility of the enzyme on sodium dodecyl sulfate/polyacrylamide gel electrophoresis, but inactivation at 37 degrees C did not affect the electrophoretic mobility. Triton X-100 effectively protected the enzyme against inactivation at 37 degrees C. The concentration required for the protection of the enzyme was more than its critical micelle concentration. Phospholipids, such as phosphatidylethanolamine, phosphatidylglycerol, cardiolipin, phosphatidylcholine, lysophosphatidylethanolamine, and lysophosphatidylcholine, also protected the enzyme against inactivation at 37 degrees C. These results suggest that the binding of hydrophobic compounds stabilizes the enzyme.

Cell Membrane↗

DNA flow cytometry on breast carcinomas: comparison of a detergent and an enzyme-detergent preparation method.

In this study we have compared two different preparation methods for DNA flow cytometry on breast cancer. Tumour cell suspensions from 49 breast cancers were analysed on a Facscan flow cytometer. In seven of 49 cases, additional aneuploid peaks were found after enzyme/detergent treatment (E/D), not seen after the detergent (D) preparation. S-Phase fractions were significantly higher after D than after E/D preparation (mean values, 15 and 8%, respectively), although the correlation was high between the two methods. S-Phase fraction estimated after background correction diminished the differences between the two methods (mean values, 8 and 6%). Furthermore, the fraction of G2/M cells were generally greater with the D method. These differences can be explained by increased number of cell doublets and nuclear fragments after D compared to E/D preparation. This clearly shows that the preparation method influences the result of DNA flow cytometry on human breast cancers.

Breast Neoplasms↗