Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The main characteristics of L-tyrosine (L-Tyr) uptake by B16/F10 malignant melanocytes are reported. This amino acid can be taken up by two systems, both of them being saturable. The first one would be system L. This system can be studied in cells preloaded with amino acids that are a good substrate for system L, such as L-methionine or L-tryptophan. The kinetic parameters for L-Tyr uptake by this transport system are Vm = 6.5 pmol L-Tyr/10(3) cells.min and Km around 130 microM. The second system, probably the system ASC, shows lower capacity but higher affinity than the former. This system can be detected only in cells previously depleted of amino acids, showing approximate kinetic values of Vm 0.05 pmol L-Tyr/10(3) cells.min and Km around 5 microM. It is shown that the increase in cell density yields a decrease in the rate of L-Tyr uptake by system L, but this increase does not affect the high affinity system, alpha-MSH does not affect significantly the L-Tyr uptake by both systems. 2-Amino bicyclo-(2,2,1)-heptane-2-carboxylic acid produces a remarkable inhibition of the rate of L-Tyr uptake, but alpha-methylaminoisobutyric acid does not affect the rate of transport of this amino acid. The absence of sodium produces a slight but reliable decrease in the rate of L-Tyr uptake, supporting the involvement of two different transport systems. The ionophores monensin and nigericin enhance the transport by system L, but this effect is suppressed by the presence of ouabain. This finding indicates that the (Na+ -K+)-ATPase is essential for the stimulating action of ionophores.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Transport of L-tyrosine by B16/F10 malignant melanocytes: characterization of the process. 198 30

Plasma-membrane vesicles prepared from the liver of rats fed either a low-(LP) or a high-protein (HP) diet exhibited Na(+)-dependent active transport of alanine and serine. The process gave apparent kinetic parameters compatible with a single saturable component for both amino acids. Na,K-ATPase (EC 3.6.1.37), marker of the basolateral domain of the hepatocyte plasma-membrane, was chosen as reference for the expression of amino acid transport in vesicle preparations. The high-protein diet induced a significant increase in liver Na,K-ATPase activity also found in corresponding plasma-membrane preparations, in parallel with an increase in the capacity towards amino acid transport. This suggests that in rats fed the high protein diet, transcellular Na+ exchange, although increased, remains well balanced. N-Methylaminoisobutyric acid (MeAIB), due to its poor velocity, proved unsuitable to distinguish between systems A and ASC in the experimental model. Comparing Na(+)- and Li(+)-driven transport, a family of carriers with strict Na(+)-dependency (A-like) was evidenced in LP vesicles but not in HP vesicles. The sensitivity to the lowering of the pH from 7.5 to 6.5 in the external medium was similar in both type of vesicles when Na+ was the driving ion. In the HP vesicles the Li(+)-tolerant, pH-insensitive component (ASC-like) was increased in parallel with overall Na(+)-dependent transport. These functional properties suggest that the carriers involved in the stimulation of transport in HP vesicles are composite in nature. Increasing concentrations of an amino acid mixture mimicking the changes of portal aminoacidemia inhibited the transport of alanine and of serine. The degree of inhibition was correlated with the relative concentration of substrate and was independent of the nutritional treatment.
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PMID:Na(+)-dependent transport of alanine and serine by liver plasma-membrane vesicles from rats fed a low-protein or a high-protein diet. 216 6

Amino acid transport was studied in C1 cells which contain amplified levels of sodium- and potassium-activated adenosine triphosphatase (Na,K-ATPase), in C4 cells which are ouabain-sensitive revertants, and in parental HeLa S3. Sodium-dependent uptake of aminoisobutyric acid and alanine was increased 2-fold in the amplified C1 cells. After a 6 h amino acid starvation period, the rate of sodium-dependent uptake of methylaminoisobutyric acid was 70-90% greater for C1 than for C4 and HeLa. This uptake was inhibitable by ouabain and the apparent Km values for high affinity uptake were similar in all three lines. Overall, neutral amino acid uptake through Systems A, ASC, and L was 2-fold higher in the Na,K-ATPase amplified C1 cells relative to C4 or HeLa. The induction of System A uptake of methylaminoisobutyric acid after starvation was more rapid in both the amplified C1 cells and the revertant C4 when compared to HeLa, which suggests that the selection for amplification of the Na,K-ATPase produced membrane alterations affecting the adaptive regulation of System A.
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PMID:Alterations in amino acid transport in Na,K-ATPase amplified HeLa cells. 300 Oct 56

The short-term protein-synthesis-independent stimulation of alanine transport in hepatocytes was further investigated. Cyclic AMP increased the Vmax. of alanine transport. Amino acid transport via systems A, ASC and N was stimulated. A good correlation was found between the initial rate of transport and the cell membrane potential as calculated from the distribution of Cl-. Cyclic AMP increased the rate of alanine transport, stimulated Na+/K+ ATPase (Na+/K+-transporting ATPase) activity and caused membrane hyperpolarization. The time courses and cyclic AMP dose-dependencies of all three effects were similar. Ouabain abolished the effect of cyclic AMP on Cl- distribution and on transport of alanine. The effect of cyclic AMP on alanine transport and Cl- distribution was mimicked by the antibiotic nigericin; the effect of nigericin was also abolished by ouabain. It is concluded that the effect of cyclic AMP on transport is mediated via membrane hyperpolarization. It is suggested that the primary action of cyclic AMP is to increase the activity of an electroneutral Na+/K+-exchange system in the liver cell plasma membrane, thus hyperpolarizing the membrane by stimulating the electrogenic Na+/K+ ATPase.
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PMID:Short-term stimulation of Na+-dependent amino acid transport by dibutyryl cyclic AMP in hepatocytes. Characteristics and partial mechanism. 303 71

Voltage-gated K+ channels are involved in regulation of action potential duration and in setting the resting membrane potential in nerve and muscle. To determine the effects of voltage-gated K+ channel expression on processes not associated with electrically excitable cells, we studied cell volume, membrane potential, Na(+)-K(+)-ATPase activity, and alanine transport after the stable expression of the Kv1.4 and Kv1.5 human K+ channels in Ltk- mouse fibroblasts (L-cells). The fast-activating noninactivating Kv1.5 channel, but not the rapidly inactivating Kv1.4 channel, prevented dexamethasone-induced increases in intracellular volume and inhibited Na(+)-K(+)-ATPase activity by 25%, as measured by 86Rb+ uptake. Alanine transport, measured separately by systems A and ASC, was lower in Kv1.5-expressing cells, indicating that the expression of this channel modified the Na(+)-dependent amino acid transport of both systems. Expression of the Kv1.4 channel did not alter alanine transport relative to wild-type or sham-transfected cells. The changes specific to Kv1.5 expression may be related to the resting membrane potential induced by this channel (-30 mV) in contrast to that measured in wild-type sham-transfected, or Kv1.4-transfected cells (-2 to 0 mV). Blocking of the Kv1.5 channel by 60 microM quinidine negated the effects of Kv1.5 expression on intracellular volume, Na(+)-K(+)-ATPase, and Na(+)-dependent alanine transport. These results indicate that delayed rectifier channels such as Kv1.5 can play a key role in the control of cell membrane potential, cell volume, Na(+)-K(+)-ATPase activity, and electrogenic alanine transport across the plasma membrane of electrically unexcitable cells.
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PMID:Influence of cloned voltage-gated K+ channel expression on alanine transport, Rb+ uptake, and cell volume. 823 76

Active glycine transport was demonstrated in microvillous (maternal-facing, BBM) and basal (fetal-facing, BCM) plasma membranes of the human term placental syncytiotrophoblast. The kinetic studies showed that the amino acid had a distinct overshoot at 1 min in BBM and 3 min in BCM vesicles while a steady state rate was achieved in approx 5 min in both the vesicles. Glycine transport is highly ion-specific and its dependency on Na+ can not be satisfied by replacing with other monovalent cation. Cl- is also implicated in the generation of the electrochemical gradient and replacement of Cl- with SO4(2-) anions failed to stimulate the transport process. The transport process was saturable with external glycine which exhibited rectangular hyperbolic kinetics typical of a mediated movement. The calculated kt and Jmax from the linear transformation of the data were 6.67 & 4 mM and 294 & 263 nmoles glycine. mg protein-1.min-1 in the BBM and BCM vesicles, respectively. The glycine transport was inhibited by a number of other amino acids which are known to be transported through the A and ASC systems. The glycine transport system may be dependent on multiple pathways such as the A, ASC or Gly which is a variant of pathway A. Glycine transport was inhibited by ouabain, a known Na+/K+ -ATPase inhibitor, in the BCM vesicles but not in the BBM system. Nicotine, insulin, sodium fluoride and sodium arsenate were inhibitors for both the vesicles.
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PMID:Transport of glycine in the brush border and basal cell membrane vesicles of the human term placenta. 893 15

The postnatal development of the subneural apparatus (SNA) and differentiation of muscle fibers of the intrinsic laryngeal muscles (ILMs) in the rat were investigated on the 1st, 5th, 15th, 30th and 90th days after birth. The cricothyroid (CT), thyroarytenoid (TA) and posterior cricoarytenoid (PCA) muscles in the ILMs were examined. Furthermore, we compared the development of these muscles with that of the skeletal muscles of the hindlimb, the extensor digitorum longus (EDL) and soleus (SOL) muscles. The SNA was observed with a scanning electron microscope. The SNA was quantitatively analyzed by use of two parameters: the ratio of the length of the secondary synaptic cleft to its maximal width (L/W ratio) and the ratio of the area of the secondary synaptic clefts to that of the primary synaptic cleft(s) (ASC/APC ratio). The muscle fiber types were classified according to the density of each muscle fiber by the ATPase stain. On the 15th postnatal day, the SNAs of the CT and TA muscles had a tendency to show more advanced development than those of the PCA muscle. The SNAs of the ILMs appeared to develop earlier than those of the EDL and SOL muscles. The L/W and ASC/APC ratios of the ILMs inclined to be higher than those of the hindlimb muscles. On the 30th day, the SNAs of the PCA muscle were still immature, while those of the CT and TA muscles had become nearly mature. The EDL muscle showed completely mature development and outstripped the ILMs. In contrast, the SNA of the SOL muscle was the least mature of all muscles. The L/W ratios of the ILMs were not significantly different from each other, while the ASC/APC ratio of the PCA muscle was significantly lower than those of both the CT and TA muscles. The L/W and ASC/APC ratios of the EDL muscle were the highest of all muscles examined and those of the SOL muscle were the lowest. The muscle fiber types were not significantly different in the ILMs throughout the course. On the 30th day, the EDL muscle had reached the mature adult proportion of the muscle fiber types, while the ILMs and SOL muscle needed further development. Phylogenetically, the TA muscle appeared as a sphincter of the lower airway and then the PCA muscle, as a dilator, appeared. The CT muscle arose after separation of the thyroid and cricoid cartilages. These findings infer that the lag in development of the PCA to the TA muscle in early postnatal life was due to the importance of the protective function of the lower airway and the phylogenetical difference. Moreover, these results suggest that the ILMs, which are indispensable for sucking, develop early in life, followed by rapid development of the EDL muscle to start quadruped walking after the 15th day. Thus, different muscles need to develop as an animal grows because distinct functions of muscles are necessary for normal living. In conclusion, the ILMs may have a specific mode of postnatal development in contrast with those of the hindlimb muscles.
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PMID:[Morphological development of the intrinsic laryngeal muscles in rat--a scanning electron microscopic and histochemical study]. 907 Nov 25

Escherichia coli CopA is a Cu(I)-translocating P-type ATPase that is involved in copper export and resistance. It is an orthologue of the human Menkes and Wilson disease-related proteins. Each of those two human copper pumps has six N-terminal Cys(X)(2)Cys sequences, but their function in transport is unclear. CopA has two N-terminal Cys(X)(2)Cys sequences, GLSC(14)GHC(17) and GMSC(110)ASC(113). The requirement of these cysteine motifs was investigated by mutagenesis of the codons for all four cysteine residues, singly and in combination. Cells of a copA deletion strain expressing genes for the mutant genes were nearly as resistant to copper as the wild type. In addition, everted membrane vesicles from cells expressing the mutant copA genes exhibited ATP-coupled accumulation of copper similar to that of the wild type. The results indicate that neither of two N-terminal Cys(X)(2)Cys motifs is required for either resistance or transport.
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PMID:Escherichia coli CopA N-terminal Cys(X)(2)Cys motifs are not required for copper resistance or transport. 1150 54

The CATERPILLER (CLR/NLR) gene family encodes a family of putative nucleotide-binding proteins important for host defense. Although nucleotide binding is thought to be central to this family, this aspect is largely unstudied. The CATERPILLER protein cryopyrin/NALP3 regulates IL-1beta processing by assembling the multimeric inflammasome complex. Mutations within the exon encoding the nucleotide-binding domain are associated with hereditary periodic fevers characterized by constitutive IL-1beta production. We demonstrate that purified cryopyrin binds ATP, dATP, and ATP-agarose, but not CTP, GTP, or UTP, and exhibits ATPase activity. Mutation of the nucleotide-binding domain reduces ATP binding, caspase-1 activation, IL-1beta production, cell death, macromolecular complex formation, self-association, and association with the inflammasome component ASC. Disruption of nucleotide binding abolishes the constitutive activation of disease-associated mutants, identifying nucleotide binding by cryopyrin as a potential target for antiinflammatory pharmacologic intervention.
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PMID:Cryopyrin/NALP3 binds ATP/dATP, is an ATPase, and requires ATP binding to mediate inflammatory signaling. 1748 56

The adaptor protein ASC (also called TMS1) links certain NLR proteins (e.g., NLRC4, NLRP3) and caspases. It is involved in the chemosensitivity of tumor cells and inflammation. Here, we found that ASC activation using NLRC4 mimicry or an autoinflammatory disease-associated NLRP3 mutant induced necrosis in COLO205 colon adenocarcinoma cells, but induced caspase-8-dependent apoptosis in NUGC-4 stomach cancer cells. As the Fas ligand induced caspase-8-dependent apoptosis in COLO205 cells, caspase-8 was intact in this cell line. ASC-mediated necrosis was preceded by lysosomal leakage, and diminished by inhibitors for vacuolar H(+)-ATPase, cathepsins, and calpains but not by inhibitors for caspase-8, or aspartic proteases, suggesting that lysosomes and certain proteases were involved in this process. Finally, growing tumors of transplanted human cancer cells in nude mice were eradicated by the activation of endogenous ASC in the tumor cells, irrespective of the form of cell death. Thus, ASC mediates distinct forms of cell death in different cell types, and is a promising target for cancer therapy.
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PMID:Activation of ASC induces apoptosis or necrosis, depending on the cell type, and causes tumor eradication. 2050 May 18


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