The influence of temperature-induced phase changes on the kinetics of respiratory and other membrane-associated enzyme systems

Raison, John K.

doi:10.1007/bf01516063

Cited by 280 publications

(56 citation statements)

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“…Other physical properties of phospholipids also have a profound influence on the activity of many membrane enzyme systems (19). For example, in the case of the cytochrome b5-cytochrome b5 reductase system it has been shown (20) that the interaction of the two enzymes depends on the translational diffusion of enzymes in the phospholipid bilayers, and hence it depends on the fluidity of the membranes.…”

Section: Discussionmentioning

confidence: 99%

Rapid conformational changes of cytochrome P -450: Effect of dimyristoyl lecithin

Tsong

Yang²

1978

Proc. Natl. Acad. Sci. U.S.A.

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Binding of benzphetamine to purified microsomal cytochrome P450 from rat liver causes a shift in the heme spin state of the protein to favor the high-spin form. This shift is strongly temperature dependent. A rapid temperature jump of a cytochrome P450/e benzphetamine mixture, monitored by changes in the Soret absorptions of the heme, reveals two relaxation processes: one in a 50-msec time range (7f) and the other in a 0.3-sec time range (T5). Both relaxations reflect conformational changes of the protein after the substrate binding. No bimolecular reaction of benzphetamine and the enzyme has been resolved. This indicates that there is no absorption change of the heme associated with the initial binding. In the presence of dimyristoyl lecithin, at 250C Tf decreases by nearly one order of magnitude whereas r, decreases to one-third. The enhancement of rates by added phospholipid is both temperature-and concentration-dependent: rates are accelerated only above the gel-liquid crystalline transition temperature, and this effect saturates near the enzyme/lipid ratio of 1:20. In contrast, the lipid does not have significant effect on the equilibrium binding curve of the substrate. These results suggest that the lipid may form an envelope around the enzyme and, depending on its crystalline state, regulates the rate of the substrate-induced conformational changes of cytochrome P450.Several factors are known to affect the equilibrium between the high-and low-spin states of cytochrome P-450 (P-450). The equilibrium shifts toward the high-spin state upon binding with certain substrates or when the temperature is increased. Equilibrium constants and other thermodynamic parameters have been calculated for P-450 from the soil bacterium Pseudomonas putida, whose high-and low-spin states are characterized by Soret bands around 391 and 417 nm, respectively (1,2). The assignment of the spin states and the point of equilibrium is less certain in liver microsomal P-450. Haugen and Coon (3) have purified, from rabbit liver microsomes, a low-spin form of P-450 with a Soret band at 418 nm and another species of P-450 that is predominantly in the high-spin state with a Soret band at 395 nm. Rein et al. (4) have shown that in the presence of benzephetamine the heme group of P-450 shifts toward the fiigh-spin state. Ebel et al. (5) have reported that, at room temperature, 40% of the P-450 in rat liver microsomes is in the high-spin state, and an additional 35% is converted to the high-spin form upon binding with substrates. They have also reported the temperature-induced difference spectrum to be a typical "type I" binding spectrum (6).We have obtained similar results with highly purified P-450 preparations. This provides an excellent system for investigating the molecular basis of the spectral and spin state changes by the The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this f...

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Section: Discussionmentioning

confidence: 99%

Rapid conformational changes of cytochrome P -450: Effect of dimyristoyl lecithin

Tsong

Yang²

1978

Proc. Natl. Acad. Sci. U.S.A.

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“…U p to this time a nonlinear Arrhenius plot for delayed light emission decay has not been reported for any other material. Other processes in plants vary in a discontinuous manner with temperature and in many cases this is correlated with changes in membrane lipid fluidity (Raison, 1973). Succinate oxidation activity in chill-insensitive plants (potato tubers, cauliflower buds and beet root) vary in a monotonic fashion, while in chill-sensitive plants (tomato fruit, sweet potato and cubumber fruit) in a discontinuous manner with temperature (Lyons and Raison, 1970;Raison et al, 1971).…”

Section: Introductionmentioning

confidence: 99%

TEMPERATURE DEPENDENCE OF DELAYED LIGHT EMISSION IN THE 6 to 340 MICROSECOND RANGE AFTER A SINGLE FLASH IN CHLOROPLASTS

Jursinic

1977

Photochem & Photobiology

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Abstract-The delayed light emission decay rate (up to 120~s) and the rise in chlorophyll a fluorescence yield (from 3 to 35 ys) in isolated chloroplasts from several species, following a saturating 10 ns flash, are temperature independent in the CL35"C range. However, delayed light in the 120-340ps range is temperature dependent. Arrhenius plots of the exponential decay constants are: (a) linear for lettuce and pea chloroplasts but discontinuous for bush bean (12-17°C) and spinach (12-20°C) chloroplasts; (b) unaffected by 3-(3,4 dich1orophenyl)l ,1-dimethylurea (inhibitor of electron flow), gramicidin D (which eliminates light-induced membrane potential) and glutaraldehyde fixation (which stops gross structural changes).The discontinuities, noted above for bush bean and spinach chloroplasts, are correlated with abrupt changes in (a) the thylakoid membrane lipid fluidity (monitored by EPR spectra of 12 nixtroxide stearate, 12 NS) and (b) the fluidity of extracted lipids (monitored by differential calorimetry and EPR spectra of 12 NS). However, no such discontinuity was observed in (a) chlorophyll a fluorescence intensity of thylakoids and (b) fluorescence of tryptophan residues of delipidated chloroplasts.Microsecond delayed light is linearly dependent on light intensity at flash intensities as low as one quantum per 2 x lo4 chlorophyll molecules. We suggest that this delayed light could originate from a one quantum process in agreement with the hypothesis that recombination of primary charges leads to this light emission. A working hypothesis for the energy levels of Photosystem I1 componcnts is proposed involving a charge stabilization step on the primary acceptor side, which is in a lipid environment.Finally, the redox potential of P680 (the reaction center for chlorophyll of system 11) is calculated to he close to 1.&1.3V.

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“…The magnitude of the activation energy for RNA transport in the presence of ATP (12.97 ± 1.45 kcal/mol) is very similar to that of the activation energies for functional ATPases. For example, beef heart mitochondrial ATPase has an activation energy of 12.8 kcal/mol (14), and the oligomyosin-insensitive rat liver mitochondrial ATPase, an activation energy of 13 kcal/mol (15). Furthermore, we have found a linear relationship with a very high product-moment correlation coefficient (>0.98) between the decline in energy charge of nucleotide additives and RNA transport in the rat liver system (unpublished results).…”

Section: Methodsmentioning

confidence: 63%

Activation energy for RNA transport from isolated rat liver nuclei.

Clawson¹,

Smuckler²

1978

Proc. Natl. Acad. Sci. U.S.A.

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ABSTRACr The temperature dependence of ATP-enhanced RNA delivery from rat liver nuclei to a surrogate cytoplasm was investigated. Examination of linear-rate data on Arrhenius graphs of l/T vs. log (% RNA delivered per min) revealed an activation energy of 12.5-13 kcal/mol. When data derived from longer incubation periods was displayed on Arrhenius graphs, we observed a discontinuous graph-two distinct linear segments with slopes of differing sign which intersected near 20°C. It was demonstrated that this discontinuity was not due to lipid phase transition in the nuclear membranes and that its position depended upon treatment of the nuclei and upon additives to the incubation mixtures. The decline in transport apparent in the upper-temperature domain on 20-min Arrhenius graphs was shown to be based on the diffusion of transported macromolecular RNA back into the nucleus-a process greatly amplified by the rapidity of transport in this domain. The large net inward diffusion, in concert with significantly differing activation energies for RNA transport and passive diffusion, suggests that the process of nucleocytoplasmic RNA transport is not diffusion driven. Our data have established that an integral parameter of RNA transport (namely, the activation energy) remains unchanged in various in vitro manipulations.Numerous in vitro assay systems for the nuclear transport of RNA have been reported. Schneider's (1) model demonstrated the effects of nucleotides on the rate of RNA release. Many other investigators (2-12) have employed variant systems to define the effects of added factors-e.g., cell-sap components (7, 9), chelating agents (10, 12), detergents (7), and metabolic inhibitors (1, 12)-on both the rate of RNA transport and the properties of the released material (2, 3). Although the influence of added nucleoside triphosphates upon the RNA transport rate has been confirmed (2)(3)(4)(5)8) KCl, MgCl2, mercaptoethanol). This suspension was laid over a "cushion" of 2.3 M sucrose buffer and centrifuged in an SW27 rotor at 95,000 X g for 75 min at SOC (13). Nuclei were recovered after passage through the 2.3 M sucrose buffer, resuspension in 0.88 M RNase-free sucrose (pH 7.6) containing 50mM 5 mM MgCl2, and 25 mM KC1, and dilution to a protein concentration of 7.4 mg/ml. To isolate detergent-treated nuclei, we added a solution of Triton X-100 (Packard Instruments) and Nonidet P-40 (Shell Oil) (final concentrations, both 0.5%) to the nuclear suspension; the material was mixed thoroughly with a Vortex mixer. The nuclei were resedimented at 600 X g for 10 min at 0C. The nuclei were again resuspended to the original volume in 0.88 M sucrose buffer.Preparation of Cell Sap. Cell sap was prepared as the 105,000 X g-supernatant fraction of the liver homogenate which was dialyzed against 0.88 M sucrose buffer overnight before use. Cell sap preparations were used fresh at final concentrations of 8-10 mg of protein per ml.RNA Release Assay. Nuclei at a final protein concentration of 3.7 mg/ml were incubated with 0.88 M sucrose ...

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The influence of temperature-induced phase changes on the kinetics of respiratory and other membrane-associated enzyme systems

Cited by 280 publications

References 44 publications

Rapid conformational changes of cytochrome P -450: Effect of dimyristoyl lecithin

Rapid conformational changes of cytochrome P -450: Effect of dimyristoyl lecithin

TEMPERATURE DEPENDENCE OF DELAYED LIGHT EMISSION IN THE 6 to 340 MICROSECOND RANGE AFTER A SINGLE FLASH IN CHLOROPLASTS

Activation energy for RNA transport from isolated rat liver nuclei.

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