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)

Adenosine triphosphatase enzymatic activity was investigated in human approximatively normal, dysplastic and neoplastic mammary tissue, by three different methods. Staining intensity varied within wide limits; myoepithelial cells and blood vessels showed similar enzymatic activity. Epithelial cells reacted only faintly, or not at all; carcinoma cells were never labelled. Stromal response was highly variable. The calcium-cobalt method of Padykula and Herman gave more intense reactions than the lead-nitrate procedure of Wachstein and Meisel, either in the original form or according to the modifications recommended by Russo and Wells. With the latter method the sharpness of stain deposits on the different structures was markedly enhanced. The functional significance of ATPase activity is discussed.
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PMID:ATPase activity in the breast: a comparison between three methods. 9 Dec 95

To study sphingolipid function(s) in Saccharomyces cerevisiae, we have investigated the effects of environmental stress on mutant (SLC) strains (R. C. Dickson, G. B. Wells, A. Schmidt, and R. L. Lester, Mol. Cell. Biol. 10:2176-2181, 1990) that either contain or lack sphingolipids, depending on whether they are cultured with a sphingolipid long-chain base. Strains lacking sphingolipid were unable to grow at low pH, at 37 degrees C, or with high salt concentrations in the medium; these environmental stresses are known to inhibit the growth of some S. cerevisiae strains with a defective plasma membrane H(+)-ATPase. We found that sphingolipids were essential for proton extrusion at low pH and furthermore found that cells lacking sphingolipid no longer exhibited net proton extrusion at normal pH after a 1-min exposure to pH 3. Cells lacking sphingolipid appeared to rapidly become almost completely permeable to protons at low pH. The deleterious effects of low pH could be partially prevented by 1 M sorbitol in the suspension of cells lacking sphingolipid. Proton extrusion at normal pH (pH 6) was significantly inhibited at 39 degrees C only in cells lacking sphingolipid. Thus, the product of an SLC suppressor gene permits life without sphingolipids only in a limited range of environments. Outside this range, sphingolipids appear to be essential for maintaining proton permeability barriers and/or for proton extrusion.
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PMID:Phenotypes of sphingolipid-dependent strains of Saccharomyces cerevisiae. 142 41

A rat kidney- and intestine-specific cDNA (D2) that induces high-affinity, Na(+)-independent uptake of cystine and dibasic and neutral amino acids into cRNA-injected Xenopus oocytes was recently isolated by expression cloning in our laboratory (R. G. Wells and M. A. Hediger. Proc. Natl. Acad. Sci. USA 89: 5596-5600, 1992). At present it is not known whether the D2-encoded protein functions as a transporter or as a transporter activator. To gain more insight into the role of D2 in renal amino acid transport, we studied the site of its expression in the kidney. This was determined by Northern blot analysis and by using a combination of in situ hybridization and immunocytochemistry with antibodies that recognize specific proximal tubule segments. D2 antisense RNA hybridized to the same tubular segments that were strongly positive for anti-ecto-adenosinetriphosphatase but negative for carbonic anhydrase type IV and the facilitated glucose transporter GLUT2. We conclude that D2 mRNA is strongly expressed in the rat kidney proximal tubule S3 segment, although there is weak hybridization to the S1 and S2 segments. The signal is absent in all other parts of the kidney. The S3 specific expression of D2 mRNA coincides with the site of high-affinity transport of cystine and other amino acids, consistent with the proposed involvement of D2 in these processes.
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PMID:Expression of mRNA (D2) encoding a protein involved in amino acid transport in S3 proximal tubule. 148 85

Previous experiments demonstrated that two thiols of skeletal myosin subfragment 1 (SF1) could be oxidized to a disulfide bond by treatment with a 2-fold excess of 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) in the presence of MgADP [Wells, J. A., & Yount, R. G. (1980) Biochemistry 19, 1711-1717]. The resulting characteristic changes in the ATPase activities of SF1 and the fact that MgADP was stably trapped at the active site [Wells, J. A., & Yount, R. G. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 4966-4970] suggested that the two thiols cross-linked were SH1 (Cys-707) and SH2 (Cys-697) from the myosin heavy chain. To verify this suggestion, SF1, after DTNB treatment as above, was treated with an excess of N-ethylmaleimide to block all accessible thiols. The single protein disulfide produced by DTNB oxidation was reduced with dithioerythritol and the modified SF1 internally cross-linked with equimolar [14C]p-phenylenedimaleimide (pPDM) in the presence of MgADP. After extensive trypsinization, the major 14C-labeled peptide was isolated, characterized, and shown to be Cys-Asn-Gly-Val-Leu-Gly-Ile-Arg-Ile-Cys-Arg, in which the two cysteines were cross-linked by pPDM. This peptide is known to contain SH2 and SH1 in this order and to come from residues 697-708 in the rabbit skeletal myosin heavy chain [Elzinga, M., & Collins, J. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 4281-4284; M. Elzinga, personal communication].(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Flexibility of the myosin heavy chain: direct evidence that the region containing SH1 and SH2 can move 10 A under the influence of nucleotide binding. 323 15

A facile and high-yield synthesis of a new ATP analogue, 2-[(4-azido-2-nitrophenyl)amino]ethyl triphosphate (NANTP), is described. NANTP and ATP are hydrolyzed by skeletal myosin subfragment 1 (SF1) at comparable rates in the presence of Ca2+, Mg2+, or NH4+-EDTA. NANTP is also cleaved but less readily by mitochondrial F1-ATPase and by (Na+ + K+)-ATPase from dog brain and hog kidney. F-Actin markedly activates NANTP cleavage by SF1 in the presence of Mg2+, suggesting that the diphosphate product NANDP is slow to be released from the enzyme. [alpha-32P]NANDP binds to a single site on SF1 (KA = 1 X 10(6) M-1) with an affinity identical with that of ADP. The absorption maximum of NANDP was shifted from 474 to 467 nm upon binding to SF1, suggesting that the purine binding site has a dielectric constant of about 45. NANDP was trapped in nearly stoichiometric amounts at the active site by cross-linking SH1 and SH2 with N,N'-p-phenylenedimaleimide (pPDM) or by chelation with cobalt (III) phenanthroline [Wells, J., & Yount, R. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 4966]. The trapped [beta-32P]NANDP X SF1 complex, like the comparable ADP X SF1 complex, was stable for days at 0 degree C and could be purified free of extraneous analogue by ammonium sulfate precipitation and gel filtration. Photolysis of the purified complex gave greater than 50% covalent incorporation of the trapped NANDP into the 95-kilodalton (kDa) heavy chain of SF1. Limited trypsinization and analysis by gel electrophoresis showed that greater than 95% of the bound label was associated with the 25-kDa NH2-terminal peptide. Without trapping, NANDP labeling of SF1 was nonspecific and was not prevented by addition of a large excess of ATP. This new approach of trapping photoaffinity analogues by cross-linking agents before photolysis may prove to be of general usefulness in increasing the specificity and extent of labeling of enzymes that undergo substrate-induced conformation changes.
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PMID:2-[(4-Azido-2-nitrophenyl)amino]ethyl triphosphate, a novel chromophoric and photoaffinity analogue of ATP. Synthesis, characterization, and interaction with myosin subfragment 1. 407 91

Myosin subfragment 1 ((S-1) is inactivated upon incubation with the nucleotide analogue 5'-p-fluorosulfonylbenzoyladenosine (5'-FSO2BzAdo). The rate of inactivation is increased in the presence of MgADP and MgPPi and decreased in the presence of MgATP. Complete loss of ATPase activity correlates with the loss of two sulfhydryl groups on S-1, and for reactions carried out in the presence of MgADP, this is accompanied by noncovalent trapping of the nucleotide (0.75 ADP/S-1). Treatment of the inactivated S-1 with dithiothreitol leads to the recovery of the lost sulfhydryl groups, release of the trapped MgADP, and recovery of the protein's activity. Importantly, all of these changes are achieved without any significant release of the incorporated radioactive nucleotide analogue. Remarkably similar results were obtained for the reaction of 5,5'-dithiobis-(2-nitrobenzoic acid) with S-1 (Wells, J. A., and Yount, R. G. (1980) Biochemistry 19, 1711-1717) and were interpreted in terms of disulfide bond formation between the reactive SH1 and SH2 thiols. It is proposed that the inactivation of S-1 by 5'-FSO2BzAdo is caused by a two-step reaction involving the initial formation of a thiosulfonate, with the SH1 group, followed by a displacement of the analogue by the SH2 residue to yield a disulfide. The stable and measurable incorporation of the analogue into S-1 proceeds in a parallel reaction at site(s) which did not affect the ATPase activity. The general feasibility of the proposed role of 5'-FSO2BzAdo in forming a disulfide bond in proteins is demonstrated by monitoring its reaction with free cysteine. As detected by pH stat titrations, 5,5'-dithiobis-(2-nitrobenzoic acid) titrations, and amino acid analysis, 5'-FSO2BzAdo rapidly converts cysteine into cystine.
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PMID:5'-p-Fluorosulfonylbenzoyladenosine. Inactivation of myosin subfragment 1 and a model reaction with cysteine. 612 9

3'-O-(4-Benzoyl)benzoyl-ATP (Bz2ATP), an analog of ATP containing a photoreactive benzophenone moiety, was used as a probe of the ATP binding site of myosin subfragment 1 (SF1). The inactivation of SF1 NH+4-EDTA ATPase by the bifunctional thiol crosslinking system cobalt(II)/cobalt(III) phenanthroline complexes was enhanced by Bz2ATP to the same degree as by ATP. This treatment resulted in the stable trapping of Bz2ATP at the active site in nearly stoichiometric amounts in a manner exactly analogous to ATP (Wells, J.A., and Yount, R.G. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 4966-4970). Irradiation of SF1 containing trapped [3H]Bz2ATP gave approximately 50% covalent incorporation of the trapped nucleotide into the enzyme. Analysis of photolabeled SF1 by gel electrophoresis showed that all of the [3H]Bz2ATP was attached to the 95-kDa heavy chain fragment. No label was found in the light chains. Similar analysis of the same protein after limited trypsin treatment demonstrated that approximately 75% of the [3H]Bz2ATP was bound to the central 50-kDa peptide and its 75-kDa precursor from the heavy chain. The N-terminal 25-kDa tryptic peptide, shown to be photolabeled by other ATP analogs (Szilagyi, L., Balint, M., Sreter, F.A., and Gergely, J. (1979) Biochem. Biophys. Res. Commun. 87, 936-945; Okamoto, Y., and Yount, R.G. (1983) Biophys. J. 41, 298a), was not labeled (less than 1%) by Bz2ATP. These results demonstrate that portions of the 50 kDa-peptide of the heavy chain are within 6-7 A of the ATP binding site on SF1 and possibly contribute to nucleotide binding.
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PMID:Photochemical probes of the active site of myosin. Irradiation of trapped 3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate labels the 50-kilodalton heavy chain tryptic peptide. 623 30

The kinetics of tryptic breakdown of the heavy chain of chymotryptic myosin subfragment 1 (S1) according to the following scheme (where the numbers represent approximate masses in kDa) are altered at 21 degrees C by divalent (Formula: see text) cations (Me2+) and by ATP, ADP, adenosine 5'-[beta, gamma-imino]triphosphate or PPi, with or without Me2+. ATP or its analogs slow step 2 and accelerate steps 3 and 4, while Me2+ accelerates step 2. ATP and its analogs decrease the amount of a transient 27-kDa peptide [Hozumi, T. & Muhlrad, A. (1981) Biochemistry 20, 2945-2950]. We have found direct evidence for the suggestion in this reference that the 27-kDa peptide is not an obligatory precursor of the 25-kDa fragment and that ATP or ADP suppresses the formation of the larger N-terminal fragment rather than accelerates its breakdown. Cross-linking of sulfhydryl groups located in the 20-kDa fragment leads to trapping of MgADP in the N-terminal 25-kDa peptide [Wells, J.A. & Yount, R.G. (1980) Biochemistry 19, 1711-1717]; this process affects the tryptic fragmentation of S1 similarly to, but less effectively than, nucleotides. Acts-S1 formation prevents the effect of ATP on fragmentation. At 37 degrees C S1 loses ATPase activity; tryptic digestion proceeds more rapidly and the 50-kDa and 25-kDa fragments are degraded to small peptides. Nucleotides protect against the effects of higher temperature by producing conformational changes not only in the 27-kDa N-terminal portion (containing the putative nucleotide binding site) of the heavy chain of S1 but also in the 50-kDa peptide.
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PMID:Effect of nucleotides, divalent cations and temperature on the tryptic susceptibility of myosin subfragment 1. 638 29

Recent experiments [Wells, J., & Yount, R. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 4966] have shown it is possible to trap MgADP and other nucleotides stably at the active site of myosin by cross-linking two thiol groups. A variety of cross-linking reagents including chelation of the two thiols by cobalt (III) phenanthroline or covalent reaction with N,N'-p-phenylenedimaleimide (pPDM) are effective trapping agents. No trapping of nucleotides occurs in the absence of divalent metals. Thus far Mg2+, Mn2+, Co2+, Ni2+, and Ca2+ but not Zn2+ all function to promote trapping of the 1:1 divalent metal-ADP complex and to enhance the rate of ATPase inactivation. Substitution-inert Cr(III) complexes of ADP, ATP, or pyrophosphate that bind very weakly or not at all to the active site are not trapped by cross-linking. While the stability of the trapped divalent metals varies, e.g., t1/2 of 0.5-7 days at 0 degree C, they are stable enough to permit accurate spectral measurements of the Mn2+ and Co2+ trapped complexes. Electron paramagnetic resonance (EPR) measurements of Mn2+ bound to 5'-adenylyl imidodiphosphate or complexed to myosin chymotryptic subfragment 1 indicate that the metal is bound at the active site. Circular dichroism (CD) and visible absorption studies of the Co2+ . ADP trapped complex indicate the metal ion is in an asymmetric octahedral environment. EPR and CD measurements show that the environment of the metal nucleotide is the same whether bound reversibly or stably trapped at the active site.
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PMID:Trapping of transition metal-nucleotide complexes in myosin subfragment 1 by cross-linking thiols; divalent transition metal probes of the active site. 682 40

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