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

---

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

The potassium-translocating Kdp-ATPase of Escherichia coli shares common functional properties with eukaryotic P-type ATPases. The KdpB subunit has been identified as the catalytic subunit forming the phosphorylated intermediate. Substitution of Asp-307 in KdpB by Glu, Asn, Gln, Tyr, His, Ala or Ser by site-directed mutagenesis and the subsequent transfer of the point mutations to the chromosome revealed that the mutants were not functioning with respect to cell growth at low K+ concentrations and ATPase activity as well as phosphorylation capacity of the purified Kdp complex. These findings indicate that Asp-307 in KdpB is the phosphorylation site of the Kdp-ATPase. In contrast, replacement of the close but non-conserved Asp-300 by Asn or Glu has no immediate influence on the enzyme functions tested. However, the Km for K+ of the ATPase activity has been increased 30-fold compared with the wild-type enzyme.
...
PMID:The phosphorylation site of the Kdp-ATPase of Escherichia coli: site-directed mutagenesis of the aspartic acid residues 300 and 307 of the KdpB subunit. 147 95

The roles of the Escherichia coli H(+)-ATPase (FoFl) delta subunit (177 amino acid residues) was studied by analyzing mutants. The membranes of nonsense (Gln-23----end, Gln-29----end, Gln-74----end) and missense (Gly-150----Asp) mutants had very low ATPase activities, indicating that the delta subunit is essential for the binding of the Fl portion to Fo. The Gln-176----end mutant had essentially the same membrane-bound activity as the wild type, whereas in the Val-174----end mutant most of the ATPase activity was in the cytoplasm. Thus Val-174 (and possibly Leu-175 also) was essential for maintaining the structure of the subunit, whereas the two carboxyl terminal residues Gln-176 and Ser-177 were dispensable. Substitutions were introduced at various residues (Thr-11, Glu-26, Asp-30, Glu-42, Glu-82, Arg-85, Asp-144, Arg-154, Asp-161, Ser-163), including apparently conserved hydrophilic ones. The resulting mutants had essentially the same phenotypes as the wild type, indicating that these residues do not have any significant functional role(s). Analysis of mutations (Gly-150----Asp, Pro, or Ala) indicated that Gly-150 itself was not essential, but that the mutations might affect the structure of the subunit. These results suggest that the overall structure of the delta subunit is necessary, but that individual residues may not have strict functional roles.
...
PMID:Escherichia coli H(+)-ATPase: role of the delta subunit in binding Fl to the Fo sector. 153 Sep 99

Site-specific mutagenesis was used to replace Gly310, Gly770, and Gly801, located in the transmembrane domain of the sarcoplasmic reticulum Ca(2+)-ATPase, with either alanine or valine. In addition, Gly310 was substituted with proline. In the Gly310----Ala mutant, the Vmax for Ca2+ transport and ATPase activity was reduced to about 40% of the wild type activity, but the apparent Ca2+ affinity was close to normal. The Gly310----Val and Gly310----Pro mutants were devoid of Ca2+ transport or ATPase activity and displayed more than a 20-fold reduction in the apparent Ca2+ affinities measured in the phosphorylation assays with either ATP or Pi. In these mutants, the rate of phosphoenzyme hydrolysis was reduced, and the ADP-insensitive phosphoenzyme intermediate accumulated. The apparent affinity for Pi was increased in the absence, but not in the presence, of dimethyl sulfoxide. The properties of this new class of Ca(2+)-ATPase mutants ("E2/E2P" type) are consistent with a conformational state in which the protein-phosphate interaction is stabilized and the Ca(2+)-protein interaction is destabilized. The Gly770----Ala mutant transported Ca2+ with a Vmax close to that of the wild type, but displayed more than a 20-fold reduction of apparent Ca2+ affinity. The Gly770----Val mutant was not phosphorylated from either ATP or Pi. The Gly801----Ala mutant transported Ca2+ with a Vmax of 126% that of the wild type, hydrolyzed ATP at the same Vmax as the wild type in the presence of calcium ionophore, and displayed a 3-fold reduction in apparent Ca2+ affinity. The Gly801----Val mutant was unable to transport Ca2+ and to be phosphorylated from ATP, even at a Ca2+ concentration of 1 mM, but Ca2+ in the micromolar range inhibited phosphorylation from Pi. The ability to bind ATP with normal affinity was retained. The properties of this mutant are consistent with a disruption of one of the two Ca2+ binding sites required for phosphorylation with ATP.
...
PMID:Functional consequences of alterations to Gly310, Gly770, and Gly801 located in the transmembrane domain of the Ca(2+)-ATPase of sarcoplasmic reticulum. 153 Nov 44

We have used four mutant calmodulins to study the regulation of human erythrocyte Ca(2+)-ATPase by the calmodulin-dependent pathway; the conserved Glu at position 12 in each of the four Ca(2+)-binding domains of calmodulin (Glu31, Glu67, Glu104, or Glu140) was replaced by Ala. At pCa 7, where unmodified calmodulin maximally activates the erythrocyte Ca(2+)-ATPase, all four mutants stimulated Ca(2+)-ATPase activity to the same maximal velocity. However, the concentrations of mutant calmodulins required for half-maximal activation (KCaM) were significantly higher than that for unmodified calmodulin and were strongly dependent on the domain in which the mutated Glu was located; substitution in either the first or second Ca(2+)-binding domain had little effect (2-3-fold increase in KCaM), whereas substitution in either the third or fourth domain resulted in a dramatic, 25-71-fold increase in KCaM. The same order of sensitivity was observed when the Ca2+ dependence of enzyme activation was measured at a constant 100 nM concentration of mutant calmodulin. These data point to dramatic differences in the functional significance of the replacement of the Glu at position 12 in each of the four Ca(2+)-binding domains for activation of the Ca(2+)-ATPase. The 2 Glu residues located in the carboxyl-terminal half of calmodulin (particularly Glu140) are crucial for activation of the Ca(2+)-ATPase at physiologically significant Ca2+ concentrations.
...
PMID:Regulation of the erythrocyte Ca(2+)-ATPase by mutant calmodulins with Glu----Ala substitutions in the Ca(2+)-binding domains. 153 52

The role of the N-terminal region of myosin light chain 1 (LC1) in actomyosin interaction was investigated using an IgG monoclonal antibody (2H2) directed against the N-terminal region of LC1. We defined the binding site of 2H2 by examining its cross-reactivity with myosin light chains from a variety of species and with synthetic oligopeptides. Our findings suggest that 2H2 is directed against the N-terminal region of LC1 which includes the trimethylated alanine residue at the N-terminus. In the presence of 2H2, the rate of actomyosin superprecipitation was reduced, although the extent was not. 2H2 caused a reduction in the Vmax of both myosin and chymotryptic S1(A1) actin-activated ATPase activity, while the Km appeared to be unaltered. The Mg(2+)-ATPase activity of myosin alone was also unaffected. Binding studies revealed that 2H2 did not prevent the formation of acto-S1 complex, either in the presence or in the absence of ATP, nor did it affect the ability of ATP to dissociate S1 from F-actin. Our findings suggest that the N-terminal region of LC1 is not essential for actin binding but is involved in modulating actin-activated ATPase activity of myosin.
...
PMID:Uncoupling of actin-activated myosin ATPase activity from actin binding by a monoclonal antibody directed against the N-terminus of myosin light chain 1. 153 57

The plasma membrane H(+)-ATPase of the yeast Saccharomyces cerevisiae is a prototype for the mutagenic analysis of structure-function relationships in P-type cation pumps. Because a functional H+ pump is required for viability, wild-type ATPase must be maintained in the plasma membrane for normal cell growth. Our expression strategy involves a rapid switch in expression from the wild-type ATPase gene to a mutant allele followed by entrapment of the newly synthesized mutant enzyme in an internal, secretory vesicle pool. The isolated vesicles prove to be ideally suited for the study of the catalytic and transport properties of the ATPase. Work to date has focused on conserved residues in the vicinity of the aspartyl-phosphate reaction intermediate. Substitution of Asp378 with Glu, Ser, or Asn and of Lys379 with Gln prevents normal biogenesis of the mutant ATPase. The more conservative Lys379----Arg mutation was tolerated, but with a sixfold loss of activity and substantial alterations in Km for ATP and Ki for vanadate. Nonconservative replacement of Thr380, Thr382, or Thr384 with Ala led to inactive enzyme, whereas the conservative change to Ser caused a two to threefold reduction in ATP hydrolysis and H(+)-pumping. Taken together, the results are consistent with an essential role for these invariant residues in phosphate-binding and ATP hydrolysis.
...
PMID:Mutagenesis of the yeast plasma membrane H(+)-ATPase. A novel expression system. 153 99

Monolayers of the Caco-2 human intestinal cell line exhibit active and passive uptake systems for the imino acid L-proline. The active transport component is saturable and it is responsible for about two thirds of the observed flux over the nanomolar concentration range, at 37 degrees C and pH 7.4. In contrast to L-phenylalanine, specific L-proline uptake has a high degree of sodium dependency and the efficiency of the carrier system is significantly reduced when protein synthesis (cycloheximide), Na+/K(+)-ATPase (ouabain) or cellular metabolism (sodium azide) are inhibited. The expression of the L-proline carrier by Caco-2 cells was under some degree of nutritional control. Glucose deficiency, over the time scale of the experiment, had no effect. The temperature-dependence of the specific uptake process followed the Arrhenius model with an apparent activation energy of 93.5 kJ nmol-1. This pathway also displayed Michaelis-Menten concentration-dependence with a Ksdm of 5.28 mM and a maximal transport flux (Jsdmax) of 835 pmol min-1 (10(6) cells)-1. Although the passive component was unchanged, the pH of the donor phase exerted a profound effect on the active carrier component. Within the physiological pH range a local maximum efficiency was found at pH 7.4 but dramatic increases were noted as pH 5.0 was approached. In competition studies, with 100-fold excess of a second amino acid, strong inhibition of uptake was found with alpha-aminoisobutyric acid, L-alanine and L-serine whereas moderate inhibition was observed with glycine, D-proline and gamma-aminoisobutyric acid. Aromatic and branched amino acids showed weak (L-valine) or no interaction (L-phenylalanine, L-leucine) with the carrier system. These data indicate that the carrier system for the uptake of L-proline has many features in common with the A system for amino acid transport.
...
PMID:Proline uptake by monolayers of human intestinal absorptive (Caco-2) cells in vitro. 154 65

To determine whether growth hormone (GH) directly affects ammoniagenesis in the renal proximal tubule, ammonia production was measured in suspensions of isolated canine renal proximal tubule segments (IPTs) incubated with 2.5 mM L-glutamine and varying concentrations of human growth hormone (hGH). Ammonia production from IPTs significantly increased by nearly threefold in the presence of hGH (10(-6) M) at 60 min. This increase was dose dependent, with as little as 10(-9) M hGH significantly stimulating ammonia production. In addition, hGH enhanced glucose production when lactate, alanine, and succinate replaced L-glutamine as substrate. hGH significantly stimulated ammonia production when IPTs were incubated at alkalotic and neutral pH. The effect of hGH was lost at acidic pH. When hGH was added to IPTs incubated under Na(+)-equilibrated conditions, ammonia production was not different from control. hGH stimulated ouabain-sensitive Na(+)-K(+)-adenosinetriphosphatase (ATPase) activity by 8.1 +/- 1.1% in basolateral membranes isolated from IPTs. hGH stimulation of proximal tubule ammonia production from L-glutamine occurs at physiological concentrations of hGH and when the extracellular-to-intracellular Na+ gradient favors L-glutamine transport. This effect is associated with an increase in basolateral Na(+)-K(+)-ATPase activity. The data suggest a role for hGH in the regulation of renal acid-base metabolism under physiological conditions in which increased net acid excretion is important.
...
PMID:Growth hormone regulates ammoniagenesis in canine renal proximal tubule segments. 159 Apr 30

1. Membrane fractions were obtained from homogenates of olfactory rosettes from Atlantic salmon (Salmo salar) or from isolated olfactory cilia and homogenates of deciliated olfactory rosettes. 2. Specific binding of L-[3H]alanine was saturable, high-affinity, and effectively inhibited by L-threonine, L-serine and L-alanine but not by L-lysine or L-glutamic acid. Comparable results were obtained with L-[3H]serine except for the presence of a second, lower affinity, binding site for L-alanine but not L-serine. 3. Specific binding of L-[3H]alanine was inhibited by low concentrations of mercury ion, acidic pH, and high concentrations of cadmium, copper or zinc ions. Aluminum had no effect. 4. Specific binding sites for L-alanine were present in membranes from isolated cilia at a level 2-fold that of membranes prepared from the deciliated rosette. 5. Ouabain sensitive Na+, K(+)-ATPase activity was also determined in cilia preparations. This enzyme was present in cilia at a level approximately 3-fold that of membranes prepared from the deciliated rosette. 6. The results are consistent with the presence of an olfactory alanine receptor in S. salar with binding characteristics similar to those of a variety of other fish species and with a localization on olfactory cilia as well as non-ciliated receptor cell membranes.
...
PMID:L-alanine binding sites and Na+, K(+)-ATPase in cilia and other membrane fractions from olfactory rosettes of Atlantic salmon. 164 34

The role of the mammalian mesonephric kidney is not completely understood. It has been established that outpouchings of the mesonephric excretory ducts give origin to parts of the urogenital system of the adult. It is also known that mammalian mesonephric urine is formed as an ultrafiltrate. The mesonephric renal tubules have Na+/K+ adenosine triphosphatase (Na+/K+ pump), secrete phenol red, and reabsorb protein. Prior to this work, the possibility of epithelial transport of ions and metabolic substrates across mammalian mesonephric tubules had not been directly evaluated. Proximal mesonephric tubules obtained from 17 to 18-days-old rabbit embryos were isolated and perfused in vitro. Continuous intracellular electrical recordings were obtained with Ling-Gerard-type microelectrodes and a high input impedance electrometer. In tubules perfused and bathed in standard mammalian Ringer's solutions, the average transmembrane electrical cell potential difference (PD) was -43 +/- 0.5 mV (76 cells). The cellular PD decreased by 30 percent when the temperature of the bath was cooled from 37 degrees C to 30 degrees C. The cells also depolarized by 25 percent in the first five minutes of exposure to 0.1 mM ouabain. In addition, the cell PD decreased by 40 and 60 percent when the extracellular potassium concentration was raised from five to 25 and 50 mM, respectively. The uptake of glucose and alanine was similarly electrogenic (delta:1 mV/mM). The cell PD, the K+ conductance, and the electrogenicity induced by luminal exposure to 5 mM glucose or alanine are significantly lower in the mesonephric as compared to the metanephric proximal tubules of the rabbit. These observations suggest that sodium-coupled transepithelial transport mechanisms, driven by the Na+/K+ pump, are already present in the mammalian mesonephric proximal tubule. Increases in the number of Na+/K+ pumps, conductive K+ channels, and sodium-substrate cotransporters seem to be at the core of proximal tubular ontogeny.
...
PMID:Renal ontogeny: epithelial transport in the mammalian mesonephric proximal tubule. 164 30


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---