• The Korean Journal of Zoology
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• v.15 no.4
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• pp.163-182
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• 1972

The effects of caffeine on the ATPase activity and Ca uptake of the fragmented sarcoplasmic reticulum isolated from rabbit skeletal muscle were studied. The ATPase activity of the heavy fraction (2,000-8,000xG) was stimulated by caffeine while that of other lighter fractions was not. It is suggested that the enhancement of the ATPase by the caffeine treatment. The Ca uptake of the heavy and middle (10,000-20,000xG) fractions was inhibited by caffeine when measured at the medium Ca concentration higher than 200 nmoles/mg protein, while only that of the heavy fraction was inhibited when measured at the Ca concentration below 200 nmoles/mg protein. Experiments with dicumarol suggested that caffeine inhibits the Ca uptake of the mitochondria as well as that of the sarcoplasmic reticulum and that the inhibition of the Ca uptake by caffeine in the low Ca concentration in the heavy fraction is due to the inhibition of the mitochondrial Ca uptake by caffeine. It appeared highly probable that the potentiation of muscle contraction caused by caffeine is solely due to the inhibition of the Ca uptake by and to the release of the accumulated Ca from the sarcoplasmic reticulum.

• Journal of Microbiology
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• v.44 no.1
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• pp.11-22
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• 2006

Escherichia coli protein Rho is required for the factor-dependent transcription termination by an RNA polymerase and is essential for the viability of the cell. It is a homohexameric protein that recognizes and binds preferably to C-rich sites in the transcribed RNA. Once bound to RNA, it utilizes RNA-dependent ATPase activity and subsequently ATPase-dependent helicase activity to unwind RNA-DNA hybrids and release RNA from a transcribing elongation complex. Studies over the past few decades have highlighted Rho as a molecule and have revealed much of its mechanistic properties. The recently solved crystal structure could explain many of its physiological functions in terms of its structure. Despite all these efforts, many of the fundamental questions pertaining to Rho recognition sites, differential ATPase activity in response to different RNAs, translocation of Rho along the nascent transcript, interactions with elongation complex and finally unwinding and release of RNA remain obscure. In the present review we have attempted to summarize 'the knowns' and 'the unknowns' of the Rho protein revealed by the recent developments in this field. An attempt has also been made to understand the physiology of Rho in the light of its phylogeny.

• Korean Journal of Microbiology
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• v.43 no.4
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• pp.250-255
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• 2007

The RecA protein of Deinococcus radiodurans is essential for the extreme radiation resistance of this organism. The central steps involved in recombinational DNA repair require DNA-dependent ATP hydrolysis by recA protein. Key feature of RecA protein-mediated activities is the interactions with ssDNA and dsDNA. The ssDNA is the site where RecA protein filament formation nucleates and where initiation of DNA strand exchange takes place. The effect of sequence heterogeneity of ssDNA was examined in this experiment. The rate of homopolymeric synthetic ssDNA-dependent ATP hydrolysis was constant or nearly so over a broader range of pHs. For poly(dT)-dependent ATP or dATP hydrolysis, rates were generally faster, with a broader optimum between pH 7.0 and 8.0. Activities of RecA protein were affected by the ionic environment. The ATPase activity was shown to have different sensitivity to anionic species. The presence of glutamate seemed to slimulate the hydrolytic activity. Dr RecA protein was shown to require $Mg^{2+}$ ion greater than 2 mM for binding to etheno ssDNA and the binding stoichiometry of 3 nucleotide for RecA protein monomer.

• Korean Journal of Environmental Agriculture
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• v.21 no.2
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• pp.102-108
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• 2002

In order to investigate the mechanism of growth inhibition by salt stress, lettuces were grown hydroponically in three different nutrient solutions, normal and 30 mM or 50 mM $KNO_3$-added nutrient solutions, and the electrical conductivities of these solutions were 1.0, 4.5, and 6.5 dS/m, respectively. The activities of plasma and vacuolar $H^+$-ATPases in the root tissue of lettuce were measured by specific inhibitors, 100 ${\mu}M$ vanadate and 50 mM $NO_3^-$, respectively. Microsomal ATPase activity of lettuce grown in the normal nutrient solution was $356\pm1.5$ nmol/min/mg protein. When lettuces were grown in 30 mM and 50 mM $KNO_3$-added nutrient solutions, total activities of microsomal ATPases were increased by 1.6 and 1.9 times, respectively, and the increases were mainly mediated by vacuolar $H^+$-ATPase. These results show that lettuces adapt themselves to salt-stressed condition by increasing the activities of $H^+$-ATPases. Effects of various heavy metal ions were investigated on the microsomal ATPases and various metal ions at 100 $\mu M$ inhibited the activities by 10$\sim$25%. $Cu^{2+}$ showed the highest inhibitory effect on the vacuolar $H^+$-ATPase. These results suggest that lettuce increases the activities of root ATPases, specially that of vacuolar $H^+$-ATPase, in salt-stressed growth conditions and $Cu^{2+}$ could be a useful tool to control the activity of vacuolar $H^+$-ATPase.

• YAKHAK HOEJI
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• v.30 no.1
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• pp.31-41
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• 1986

Sarcolemmal membrane fraction from canine ventricle was isolated from the discarded pellet after the first homogenization in the isolation procedure of sarcoplasmic reticulum (Method 1) and the protein yield, purity, and sidedness of this preparation were compared to those of sarcolemmal fraction prepared by method of Lee et al. (Method 2) and a slight modification of original protocol of Jones et al. (Method 3). Method 1 differed from Method 2 essentially only in that vigorous homogenization was carried out by omnimixer and homogenization medium containing 30mM Tris-maleate was used in the first step. The sarcolemmal fraction was enriched from 45 to 50 and 29-fold in [$^3H$] ouabain, [$^3H$] DHA, [$^3H$] QNB binding and $Na^+$, $K^+$-ATPase activity, respectively, compared to homogenate. Total $Na^+$, $K^+$-ATPase activity of highly sarcolemma enriched fraction was 144.6$\pm$16.4$\mu\textrm{mol}$ Pi/mg protein/hr, which was about 85%, of total ATPase activity, and the yield of the preparation was 15.7 mg protein per 100g of starting ventricular tissue. The sarcolemmal preparation supported $^{45}Ca^{2+}$-uptake in the presence of ATP but this uptake was not dependent on oxalate. Sarcolemmal $Na^+$, $K^+$-ATPase activity and detectable [$^3H$] ouabain binding were increased about 32% and 35%, respectively, by pretreatment of sarcolemmal fraction with optimal concentration of sodium dodecylsulfate (0.3-0.4mg/mg protein), suggesting that this preparation contained about 24% of sealed rightside-out vesicles, 26% of sealed inside-out vesicles, and 5001o of freely permeable (leaky) form. This procedure showed the highest protein yield and leaky population, compared to Method 2 and 3. On the other hand, sarcolemmal fraction prepared by Method 2 and 3 showed low value in protein yield but comtained high population of inside-out (46%) and rightside-out (49%) vesicles, respectively, compared to present procedure (Method 1). The results indicate that vigorous homogenization decreases the population of sealed sarcolemmal vesicles but increases the sarcolemmal protein yield per gram tissue and that this procedure is available for further purification of sarcolemmal fraction and for the receptor binding study of sarcolemma.

• The Journal of Korean Medicine
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• v.17 no.2 s.32
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• pp.264-276
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• 1996

This study was carried out to evaluate the effect of Samhwasan on the Na-K-ATPase activity of heart muscle. The Na-K-ATPase activity was prepared from rabbit heart ventricles. Samhwasan markedly inhibited the Na- K - ATPase activity in a dose-dependent manner with an estimated $I_{50}$ of 0.56%. Hill coefficient was 1.70, indicating that the enzyme has more than one binding site for the Samhwasan. Inhibition of enzyme activity by Samhwasan increased as pretreatment time was prolonged. Inhibition by the drug was not affected by a change in enzyme protein concentration. Kinetic studies of substrate activation of the enzyme indicated classical noncompetitive inhibition, showing significant reduction in Vmax without a change in Km value. Inhibitory effect by Samhwasan was not altered by changes in concentration of $Mg^{2+}$, $Na^+$ or $K^+$, dithiothreitol. a sulfhydryl reducing reagent, did not protect the inhibition of Na-K-ATPase activity by Samhwasan combination of Samhwasan and ouabain showed a cumulative inhibition fashion. These results suggest that Samhwasan inhibits Na-K-ATPase activity of heart ventricles with an unique binding site different from that of ATP, $Mg^{2+}$, $Na^+$ or $K^+$ and ouabain.

• Journal of the Korean Society of Food Science and Nutrition
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• v.18 no.1
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• pp.123-130
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• 1989

Myofibrillar protein(myofibil) was prepared from Yellowtail fish (Seriola quinqueradiata), and then, it was stored at $0^{\circ}C$(ice-cooling), $-3.5^{\circ}C$(partial freezing) and $-20^{\circ}C$(freezing). Another myofibrils were prepared from the fish stored with ice-cooling, partial freezing and freezing for a week as the maximum. Denaturation of muscle protein during the storage was investigated by the measurement of $Ca^{2+}-$ and $Mg^{2+}-ATPase$ activity. Specific activity of $Ca^{2+}-\;and\;Mg^{2+}-ATPase$ associated with Yellowtail myofibrils was 0.155 and $0.149\;{\mu}\;mole$ Pi/min/mg of protein, respectively, before storgae. ATPase activity of myofibils did not show any significant difference between $0^{\circ}C$ and $-3.5^{\circ}C$ whereas it was decreased faster at $-20^{\circ}C$ than at $0^{\circ}C$ or $-3.5^{\circ}C$. ATPase activity of myofibirls extracted from the fish stored for a week was 1.2-1.8 times higher than myofibils stored with ice-cooling or partial freezing while it was 2.5-3 times higher than that with freezing. Apparent denaturation constant of $Ca^{2+}-ATPase$ of myofibrils was between 0.48-0.65, and it was 2-3 times higher than that of $Mg^{2+}-ATPase$. The constant of myofibrils extracted from the fish did not show significant difference between $Ca^{2+}-\;and\;Mg^{2+}-ATPase$.

• The Journal of Korean Medicine
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• v.16 no.1 s.29
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• pp.281-294
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• 1995

The effect of Sam Hwa San on the Na-K-ATPase activity was evaluated in microsomal fraction prepared from rabbit cerebral cortex to determine whether Sam Hwa San affects Na-K-ATPase activity of nervous system. Sam Hwa San markedly inhibited the Na-K-ATPase activity in a dose-dependent manner with an estimated $I_{50}$ of 0.12%. Optimal pH for the Na-K-ATPase activity was at 7.5 in the presence or absence of Sam Hwa San. The degree of inhibition by the drug more increased at acidic and alkalic pHs than neutral pH. Kinetic studies of substrate and cationic activation of the enzyme indicate classic noncompetitive inhibition fashion for ATP, Na and K, showing significant reduction in Vmax without a change in Km. Dithiothreitol, a sulfhydryl reducing reagent, partially protects the inhibition of Na-K-ATPase activity by Sam Hwa San. Combination of Sam Hwa San and ouabain showed higher inhibition than cumulative inhibition. These results suggest that Sam Hwa San inhibits Na-K-ATPase activity in central nervous system by reacting with, at least a part, sulfhydryl group and ouabain binding site of the enzyme protein, but with different binding site from those of ATP, Na and K.

• Molecules and Cells
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• v.40 no.12
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• pp.925-934
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• 2017

The Cdc6 protein is essential for the initiation of chromosomal replication and functions as a licensing factor to maintain chromosome integrity. During the S and G2 phases of the cell cycle, Cdc6 has been found to inhibit the recruitment of pericentriolar material (PCM) proteins to the centrosome and to suppress centrosome over-duplication. In this report, we analyzed the correlation between these two functions of Cdc6 at the centrosome. Cdc6 depletion increased the population of cells showing centrosome over-duplication and premature centrosome separation; Cdc6 expression reversed these changes. Deletion and fusion experiments revealed that the 18 amino acid residues (197-214) of Cdc6, which were fused to the Cdc6-centrosomal localization signal, suppressed centrosome over-duplication and premature centrosome separation. Cdc6 mutant proteins that showed defective ATP binding or hydrolysis did not exhibit a significant difference in suppressing centrosome over-duplication, compared to the wild type protein. In contrast to the Cdc6-mediated inhibition of PCM protein recruitment to the centrosome, the independence of Cdc6 on its ATPase activity for suppressing centrosome over-duplication, along with the difference between the Cdc6 protein regions participating in the two functions, suggested that Cdc6 controls centrosome duplication in a manner independent of its recruitment of PCM proteins to the centrosome.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.6
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• pp.725-732
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• 1998

In order to elucidate the molecular mechanism of the intracellular $Ca^{2+}$ overload frequently reported from diabetic heart, diabetic rats were induced by the administration of streptozotocin, the membrane vesicles of junctional SR (heavy SR, HSR) were isolated from the ventricular myocytes, and SR $Ca^{2+}$ uptake and SR $Ca^{2+}$ release were measured. The activity of SR $Ca^{2+}-ATPase$ was $562{\pm}14$ nmol/min/mg protein in control heart. The activity was decreased to $413{\pm}30$ nmol/min/mg protein in diabetic heart and it was partially recovered to $485{\pm}18$ nmol/min/mg protein in insulin-treated diabetic heart. A similar pattern was observed in SR $^{45}Ca^{2+}$ uptakes; the specific uptake was the highest in control heart and it was the lowest in diabetic heart. In SR $^{45}Ca^{2+}$ release experiment, the highest release, 45% of SR $^{45}Ca^{2+}$, was observed in control heart. The release of diabetic heart was 20% and it was 30% in insulin-treated diabetic heart. Our results showed that the activities of both SR $Ca^{2+}-ATPase$ and SR $Ca^{2+}$ release channel were decreased in diabetic heart. In order to evaluate how these two factors contribute to SR $Ca^{2+}$ storage, the activity of SR $Ca^{2+}-ATPase$ was measured in the uncoupled leaky vesicles. The uncoupling effect which is able to increase the activity of SR $Ca^{2+}-ATPase$ was observed in control heart; however, no significant increments of SR $Ca^{2+}-ATPase$ activities were measured in both diabetic and insulin-treated diabetic rats. These results represent that the $Ca^{2+}$ storage in SR is significantly depressed and, therefore, $Ca^{2+}-sequestering$ activity of SR may be also depressed in diabetic heart.