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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The N-terminal formic acid fragment (FA1) of the N-[3H]ethylmaleimide-labeled and carboxymethylated bovine mitochondrial phosphate transport protein (PTPN*CM) has been purified and completely sequenced: NH2-Ala-Val-Glu-Glu-Gln-Tyr-Ser-Cys-Asp-Tyr10-Gly-Ser-Gly-Arg-Phe- Phe-Ile-Leu-Cys- Gly20-Leu-Gly-Gly-Ile-Ile-Ser-Cys-Gly-Thr-Thr30-His-Thr -Ala-Leu-Val-Pro-Leu-Asp- -Leu-Val40-Lys-Cys(N-[3H]ethylmaleimide)-Arg-Met-Gln-Val-Asp- COOH. By thermolysin digestion of FA1 and high-performance liquid chromatography isolation of the radioactive subfragment Leu39-Arg43, the sole N-ethylmaleimide-binding residue has been identified as Cys42. FA1 contains a high mole percentage of cysteine (8.5%) and shows silver staining anomaly. Its sequence reveals significant homology in the triplicated gene regions (Pro27,132,229) of the mitochondrial ADP/ATP carrier from beef heart and Neurospora crassa. The hydropathic profile suggests that FA1 contains a transmembrane segment (Phe15-Val40) with only one basic (His31) and one acidic (Asp38) residue. The presence of the phosphate transport protein gene among nuclear genes is suggested from a lack of significant homology between the reverse-translated FA1 (mitochondrial codons) and the bovine mitochondrial genome. The inhibitory action of N-ethylmaleimide on the phosphate transport mechanism is discussed.
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PMID:Sequence of the N-terminal formic acid fragment and location of the N-ethylmaleimide-binding site of the phosphate transport protein from beef heart mitochondria. 406 97

1. Oxidation of sperm-whale metmyoglobin and its apoprotein with periodate has been investigated under various conditions of pH and temperature to find those under which the reagent acted with specificity. 2. At pH6.8 and 22 degrees consumption of periodate ceased in 3(1/2)hr. at 43 moles of periodate/mole of myoglobin. The two methionine residues, the two tryptophan residues, the three tyrosine residues and two histidine residues were oxidized; serine increased in the hydrolysates from 6 to 9 residues/mol. 3. At pH5.0 and 22 degrees , consumption levelled off in 4(1/2)hr. at 26 moles of periodate/mole of myoglobin and resulted in the modification of the two methionine residues, the two tryptophan residues, the three tyrosine residues and two histidine residues; serine increased from 6 to 7 residues/mol. and, also, ferrihaem suffered considerable oxidation. 4. Oxidation at pH5.0 and 0 degrees resulted at completion (4hr.) in the consumption of 22 moles of periodate/mole of myoglobin and in the modification of the methionine, tyrosine and tryptophan residues. Spectral studies indicated oxidation of the haem group. This derivative reacted very poorly with rabbit antisera to MbX (the major component no. 10 obtained by CM-cellulose chromatography; Atassi, 1964). 5. Oxidation of apomyoglobin at pH5.0 and 0 degrees was complete in 4hr. with the consumption of 7.23 moles of periodate/mole of apoprotein. The rate of oxidation in decreasing order was: methionine; tryptophan; tyrosine; and after 7hr. of reaction the following residues/mol. were oxidized: methionine, 2.0; tryptophan, 1.6; tyrosine, 0.99. No peptide bonds were cleaved. Metmyoglobin prepared from the 7hr.-oxidized apoprotein showed that the reactivity with antisera to MbX had diminished considerably. 6. Milder oxidation of apoprotein (2 molar excess of periodate, pH5.0, 0 degrees , 2hr.) resulted in the modification of 1.66 residues of methionine/mol. Metmyoglobin prepared from this apoprotein was identical with native MbX spectrally, electrophoretically and immunochemically. It was concluded that the methionine residues at positions 55 and 131 were not essential parts of the antigenic sites of metmyoglobin.
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PMID:Periodate oxidation of sperm-whale myoglobin and the role of the methionine residues in the antigen-antibody reaction. 429 93

The reversibility of adenylylation of glutamine synthetase from E. coli by adenylyltransferase was demonstrated. Several positive effectors (Gln, 2-hydroxyethyl-S-cysteine, Trp and Met) stimulate the back reaction in the same manner as the forward reaction. The apparent Michaelis constant for PP(i) is 2.2 mM at pH 7.35. The pH optimum of the back reaction is 6.5-7 while the pH optimum of the forward reaction is 7.6. The apparent equilibrium constant in the presence of 10 mM Mg(2+) at pH 7.36 is 8.5 in favor of adenylylated glutamine synthetase and PP(i). The equilibrium constant is strongly dependent from pH and from Mg(2+) concentration. There is a difference of about 0.5 to 1 kcal/mole free energy between the adenylyl-O-tyrosine bond and the pyrophosphate bond of adenosine triphosphate (ATP). It follows from these considerations that the adenylyl-O-tyrosine bond is an "energy-rich phosphate bond."
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PMID:Reversibility of the ATP:glutamine synthetase adenylyltransferase reaction. 491 Aug 53

1. Using a double-lumen tube perfusion system the rates of absorption of L-methionine and glucose from a 30 cm segment of the jejunum were estimated in eight relatively normal Zambian African subjects. The effect of each substrate on the absorption of the other has also been investigated. The solutions perfused were given at 12.0 ml. min(-1), and contained (A) 100 m-mole l.(-1)L-methionine, (B) 100 m-mole l.(-1)L-methionine and 150 m-mole l.(-1) glucose and (C) 150 m-mole l.(-1) glucose.2. The presence of glucose in the perfusing fluid did not significantly alter the mean absorption rate of methionine; in six subjects, the rate of methionine absorption from solution B was less than from solution A, but in two there was a marked difference in the opposite direction. This may indicate an individual difference in the effect of glucose on L-methionine absorption in man. The presence of methionine in the perfusing fluid did not significantly alter the mean absorption rate of glucose.3. Five subjects had a transitory psychiatric disturbance after the investigation. The cause of this is not clear, but was probably caused by the absorption of a break-down product of methionine from the large intestine.
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PMID:Intestinal absorption rate of L-methionine in man and the effect of glucose in the perfusing fluid. 501 67

Processing of RNA in the toad bladder was analyzed by polyacrylamide-gel electrophoresis to determine whether aldosterone causes any changes in the 1 hr before it potentiates transport of sodium ion. No change was found in the quantity or in the specific activity of bulk RNA labeled with uridine-5-(3)H. In vivo and in vitro with either uridine-5-(3)H or with methionine-(methyl)-(3)H as precursors, processing of RNA was extremely slow. Heterodisperse RNA was obvious after 30 min of continuous labeling, but labeling of the 40S precursor of ribosomal RNA was not apparent for 60 min. Labeling of mature 28S and 18S RNA first became apparent after 8 hr. approximately 7S RNA was the principal fastmigrating species labeled at 30 min, and 4S RNA was not heavily labeled until 1 hr. Aldosterone (5 x 10(-7) mole/liter) produced no changes. If care were not taken to inhibit metabolism of native bacteria colonizing the bladder, bacterial RNA of high specific activity predominated. We conclude that RNA metabolism in the toad bladder is extraordinarily slow, that a major acceleration of de novo synthesis in response to physiologic doses of aldosterone was not demonstrable, and that some reports to the contrary may have been influenced by artifacts from bacterial RNA metabolism. Earlier evidence for obligatory alterations in RNA metabolism during the latent period is not strong.
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PMID:Kinetics of RNA synthesis in toad bladder epithelium: action of aldosterone during the latent period. 554 20

Amyloid was extracted from the spleen of a patient with primary amyloidosis by homogenizing it at high speed with water after preliminary treatments, first to remove proteins soluble in saline, and then to remove salts. The extracts containing amyloid appeared to be clear at concentrations up to 6 mg/ml of protein. The material gave little sediment on being centrifuged up to 20,000 g for 1 hr, but the protein was sedimented at 100,000 g in 1 hr. The amyloid could be precipitated from the extracts by addition of NaCl to 0.0075 mole/liter or of CaCl(2) to 0.0025 mole/liter. The protein-bound Congo red formed a red precipitate and this property was used to estimate recovery and purity of amyloid during extraction. On electronmicroscopy the isolated amyloid proved to be morphologically pure. It existed either as single filaments measuring 60-80 A in diameter or as large aggregates of these filaments.Freshly isolated amyloid in water sedimented as a single homogeneous peak with an s degrees (20,[unk]) of about 45-50S. On standing, the solution became cloudy and more rapidly sedimenting components appeared. On electrophoresis the material migrated as a homogeneous peak towards the anode. The protein had an amino acid composition different from that of all known serum proteins. It was rich in acidic amino acids and had little cysteine and methionine and no hydroxyproline. The total content of carbohydrate was less than 2%.
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PMID:The characterization of soluble amyloid prepared in water. 564 27

The anti-tumour drug cisplatin is a potent nephrotoxic agent. Renal Na+/K+-activated and Mg2+-activated ATPases are shown to be equally sensitive to cisplatin inhibition in vitro. An aged solution of cisplatin, containing hydrolysis products, is a thousand times more inhibitory to ATPase (ID50 8.0 X 10(-7) M) than freshly made cisplatin solutions (ID50 6.5 X 10(-4) M). Chloride ion concentrations of 0-150 mM in the assay mixtures do not affect either the extent of inhibition of ATPase by cisplatin or the time required for inhibition to develop. We conclude that cisplatin reacts directly with ATPase rather than that a hydrolysis product is responsible for the inhibition. Various amino acid complexes with cisplatin were tested for their ability to inhibit ATPase. Cysteine/cisplatin in a mole ratio of 1 : 1 is completely ineffective. Mono-substituted methionine/cisplatin is more inhibitory than cisplatin alone but di-substituted methionine/cisplatin is less effective. The reason for these observations and their significance to nephrotoxicity are discussed.
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PMID:The inhibition of renal ATPase by cisplatin and some biotransformation products. 612 88

Human liver alanine aminopeptidase (EC 3.4.11.14; L-alpha-aminoacyl-peptide hydrolase) catalyzes the stepwise hydrolysis of methionyl-lysyl-bradykinin to yield methionine, lysine, and the limit nonapeptide, bradykinin which is resistant to further hydrolytic cleavage by this enzyme. Alanine aminopeptidase also catalyzes the hydrolysis of various neutral amino acid beta-naphthylamides. This enzyme cleaves N-terminal arginyl residues unless the adjacent penultimate residue is proline as is the case for bradykinin. The properties are consistent with the requirements of a kinin converting enzyme. Human alanine aminopeptidase activity is reduced by several beta-lactam antibiotics, with the cloxacillin, oxacillin, and methicillin Ki values being 0.51 mM, 1.6 mM, and 2.4 mM respectively. Our experiments with radioactively labelled penicillin indicate that two moles of antibiotic are bound per mole of enzyme. Neither chromatography of the penicillin-treated enzyme on G-25 Sephadex, treatment of penicillin-G-treated enzyme with penicillinase, nor extensive dilution of cloxacillin-treated enzyme diminished the degree of inactivation produced. Inhibition was obtained with 6-aminopenicillanic acid, which indicated that the penicillin nucleus itself was being bound, but substitutions, as in cloxacillin, could enhance the binding.
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PMID:Human-liver alanine aminopeptidase. A kinin-converting enzyme sensitive to beta-lactam antibiotics. 612 21

A radioenzymatic assay for the measurement of histamine is described, based on the incubation of histamine in the presence of histamine-N-methyl-transferase from rat kidney and [3H-methyl]-S-adenosyl-L-methionine (sp act 15 Ci/mmol) in phosphate buffer, 0.05 mole/l, pH 7.9, at 37 degrees C for 60 min. The N-[3H]-methyl]histamine generated was selectively extracted into toluene/isoamyl alcohol (3:2) and the quantity of the tritium in the sample was determined by liquid- scintillation counting. As little as 1 nmol/l of histamine can be detected. The assay is specific, with no cross-reactivity noted for several compounds closely related to histamine. The assay was used to measure the released histamine of a group of allergic subjects following the incubation of their blood with various allergens. A good correlation was found between histamine release from whole blood and the response of skin mast cells to intradermal antigen administration.
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PMID:Development of a sensitive radioassay of histamine for in vitro allergy testing. 620 58

The interaction of the myelin basic protein (MBP) and the major endogenous ganglioside GM1 in myelin of the central nervous system has been investigated using both 500-MHz 1H and 67.89 MHz 13C NMR. Titration of MBP by GM1 resulted in 13C NMR signal shifts for the I1e and His residues of MBP at a GM1/MBP mole ratio of one or less. The carbohydrate head group of GM1 was also found to be perturbed. 1H NMR results obtained in a similar manner demonstrated the perturbation of His and Phe residues. At a GM1/MBP mole ratio of 0.5, small perturbation of Trp #116 was observed, and at mole ratios of two and beyond significant involvement of Phe residues and methylated Arg #107 was found. Met #167 was more perturbed than Met #20; hence, more extensive interaction of the lipid is occurring with the C-terminus of the protein than with the N-terminus. No resonances from GM1 bound to MBP at mole ratios of up to one appeared in the spectra. However, as the GM1/MBP mole ratio was increased to eight or greater a major conformational change of MBP was detected. An upfield shift of the GM1 midchain methylene resonance was observed for the GM1/MBP complex. This observation provides strong evidence that the state of GM1 interacting with MBP is different from that of GM1 micelles. The number of saturable GM1 binding sites on MBP is estimated to be four. The data also favor a rapid exchange between bound GM1 and GM1 micelles. Interaction of MBP with the oligosaccharide derived from GM1 was found to be weaker than with GM1. Based on our data, a model for the interaction can be proposed: the first GM1 molecule is bound to the protein molecule through its head group and hydrocarbon chains, followed by the formation of a GM1/MBP complex with a concomitant conformational change of MBP as more GM1 is added.
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PMID:Interaction of ganglioside GM1 and myelin basic protein studied by carbon-13 and proton nuclear magnetic resonance spectroscopy. 620 15


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