Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Doxorubicin (adriamycin) forms molecular associations with other aromatic and planar molecules (hetero-association) and with other doxorubicin molecules (self-association) in aqueous solution. The ability of doxorubicin to form complexes was demonstrated in a nonbiological system by measuring the doxorubicin partition coefficient. A decreased apparent doxorubicin activity coefficient in the presence of complex formation was also demonstrated in a biological system by measuring the transmembranous doxorubicin transport and the doxorubicin distribution at equilibrium in human red blood cells and their suspending medium. Doxorubicin formed complexes in aqueous solution at 37 degrees (pH 7.3) with (a) DNA-derived bases, nucleosides, and nucleotides; (b) amino acids such as tryptophan; (c) proteins such as human serum albumin and hemoglobin; and (d) a broad range of biologically active compounds such as NAD, propanthelline, caffeine, chloroquine, imipramine, and propranolol. The apparent thermodynamic quantities of the complex formation with adenosine 5'-triphosphate were delta H0, -9.5 kcal . mole-1; delta S0, -19 eu . mole-1; and delta G0 (310 degrees K), -3.6 kcal . mole-1. The binding forces of the molecular associations were probably hydrophobic (short-range force), sometimes supported by electrostatic interaction (long-range force).
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PMID:Molecular association between doxorubicin (adriamycin) and DNA-derived bases, nucleosides, nucleotides, other aromatic compounds, and proteins in aqueous solution. 712 47

The dimeric enzyme tryptophanyl-tRNA synthetase from beef pancreas catalyses the stoichiometric formation of one mole of tryptophanyl-adenylate per subunit. This formation is associated with optical changes (absorbance, fluorescence, optical rotation) and is confirmed by analytical ultracentrifugation. An equal amplitude of the change is observed for each adenylation site at pH 8.0, 25 degrees C, regardless of the optical method used. The formation of two tryptophanyl adenylates per dimer corresponds to a molar absorbance change delta epsilon 291 = 12000 +/- 500 cm-1 M-1, to a fluorescence quenching of 24 per cent at 340 nm and to a variation in optical rotation of 6 per cent at 313 nm. The circular dichroic band of the adenosine moiety of ATP is strongly increased. The addition of sodium pyrophosphate to the tryptophanyl-adenylate-enzyme complex restores the absorbance and fluorescence amplitude observed prior to the addition of ATP to the enzyme. Magnesium ions are necessary to the reaction. A pertubation of the environment of both the protein and the substrates (tryptophan and ATP) have to be taken into account to explain the magnitude of the observed changes.
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PMID:Tryptophanyl-tRNA synthetase from beef pancreas. Spectroscopic analysis of the stoichiometry of formation of the enzyme-tryptophanyl-adenylate complex. 736 41

Lumazine protein, a novel protein containing 6,7-dimethyl-8-ribityllumazine as a bound prosthetic group, is one of the several major proteins produced by the bioluminescent bacteria, Photobacterium phosphoreum. purification to complete homogeneity from cell extracts is achieved in six steps. Lumazine protein is a near spherical, monomeric protein of average molecular weight 20,000; in amino acid composition it is acidic with two isoelectric isomers, pI 4.9 and 5.0, and is hydrophilic (974 cal/residue) with single methionine and tryptophan residues and two accessible cysteines. It contains no carbohydrate. Reaction of the cysteines with dithionitrobenzoic acid results in quenching of the bound lumazine fluorescence but is otherwise reversible. Estimates of protein by dry weight results in a mole ratio of one bound lumazine group per protein.
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PMID:Lumazine protein from the bioluminescent bacterium Photobacterium phosphoreum. Purification and characterization. 741 Mar 96

CHIP28 occurs naturally in glycosylated and nonglycosylated forms. The purpose of this study was to determine the role of glycosylation in CHIP28 structure and function. A new purification procedure based on phenylboronic acid-agarose (PBA) affinity chromatography was developed to isolate CHIP28. In purified native CHIP28 from erythrocytes, approximately 50% of CHIP28 molecules were glycosylated; each mole of glycosylated CHIP28 contained 5.4 kDa of monosaccharides consisting of 2 mol of Fuc, 8 mol of Gal, 1 mol of GalN, 13 mol of GlcN, 3 mol of Man, and 1 mol of Neu5Ac. The proportions of each monosaccharide and the sensitivity to endo-beta-galactosidase indicated that CHIP28 contained polylactosaminyl oligosaccharides. Glycosylated and nonglycosylated CHIP28 remained tightly associated when solubilized in octyl beta-D-glucoside (OG) and could not be separated by conventional chromatographic procedures. To remove the sugar moiety, CHIP28 was enzymatically deglycosylated by PNGase F and purified by Q-Sepharose anion-exchange and Erythrina cristagalli lectin chromatography. High-performance size-exclusion chromatography revealed that native CHIP28 eluted as an apparent dimer, whereas deglycosylated CHIP28 eluted as an apparent monomer. In reconstituted proteoliposomes, deglycosylated CHIP28 had a single channel water permeability (pf) of 3.1 x 10(-14) cm3/s (10 degrees C), not different from that of 3.2 x 10(-14) cm3/s for native CHIP28. Circular dichroism of native and deglycosylated CHIP28 in OG revealed 45% and 48% alpha-helix, respectively; intrinsic tryptophan fluorescence showed no effects of glycosylation on tryptophan environment. Freeze-fracture electron microscopy with rotary shadowing indicated that native and deglycosylated CHIP28 assembled as tetramers in reconstituted proteoliposomes.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Purification and structure-function analysis of native, PNGase F-treated, and endo-beta-galactosidase-treated CHIP28 water channels. 753 4

There is a growing consensus that altered proteins are more susceptible to degradation than native proteins. The enhancement of degradation of damaged proteins may be of significance since it prevents the accumulation of damaged proteins in cells. Several proteolytic pathways have been discovered in the lens. These include ATP-independent, ATP-dependent and ATP/ubiquitin-dependent proteolytic pathways. However, the extent of involvement of these proteolytic pathways in degradation of damaged proteins is not well described. alpha-Crystallin was oxidized by exposure to 0.03-3.2 mol.OH (mol protein)-1. Modifications to the oxidized alpha-crystallin and proteolytic susceptibility of the oxidized alpha-crystallin were studied. Exposure to > 0.32 mol.OH per mole of subunit produced aggregates and fragments of alpha-crystallin. Changes in isoelectric points of the proteins were observed after exposure to 0.64 mol.OH (mol protein)-1. The extent of loss of tryptophan and sulfhydryl groups was related to the level of .OH-exposure. Carbonyl content increased progressively with increasing oxidation. When incubated with a supernatant of bovine lens epithelial cells, the .OH-modified proteins were proteolytically degraded up to three times faster than untreated alpha-crystallin. ATP stimulated the degradation of native alpha-crystallin and alpha-crystallin which was exposed to 1.6 mol.OH (mol subunit protein)-1 (alpha 1.6). Sixty-seven per cent and 100% of the ATP-dependent degradation of native alpha-crystallin and alpha 1.6 was ubiquitin-dependent, respectively. The data indicate that alpha-crystallins oxidized by .OH are recognized and degraded rapidly by cytoplasmic proteolytic systems in bovine lens epithelial cells. Both ATP-independent and ATP/ubiquitin-dependent proteolytic pathways are involved in the degradation of native and oxidized alpha-crystallin.
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PMID:Degradation of differentially oxidized alpha-crystallins in bovine lens epithelial cells. 755 69

The major eye-lens protein alpha-crystallin is known to possess a remarkable sequence homology to the low molecular weight heat-shock proteins and has been shown to protect several proteins against thermally induced aggregation. In this work we demonstrate that the rapid aggregation of rabbit muscle phosphoglycerate kinase during incubation at 52 degrees C is completely inhibited in presence of 1/3 moles alpha-crystallin monomer per mole enzyme. Upon irradiation by UV light, tryptophan fluorescence intensity of alpha-crystallin declines, reflecting the destruction of these residues. A remarkable correlation is revealed between the reduction in alpha-crystallin fluorescence during UV-irradiation and the loss of its ability to protect phosphoglycerate kinase against aggregation. Since a loss of tryptophan fluorescence in intact eye lenses in vivo has been demonstrated to occur upon exposure to UV light, as well as during aging, it is proposed that the enhanced rate of lens opacification and cataract formation, as well as the increased levels of damaged lens proteins, which accumulate under these conditions, are the result of the gradual loss of the chaperone-protein efficacy of alpha-crystallin.
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PMID:Photodegradation of tryptophan residues and attenuation of molecular chaperone activity in alpha-crystallin are correlated. 762 28

Native calponin is able to bind 2 mol of calcium binding protein (CaBP) per mole calponin. This study extends this observation to define the 2 domains of interaction, one of which is near the actin binding site, and the other in the amino-terminal region of calponin. Also, the first evidence for a differentiation in the response of calponin to interaction with caltropin versus calmodulin is demonstrated. The binding of caltropin to cleavage and recombinant fragments of calponin was determined by 3 techniques: tryptophan fluorescence of the fragments, CD measurements to determine secondary structure changes, and analytical ultracentrifugation. In order to delineate the sites of interaction, 3 fragments of calponin have been studied. From a cyanogen bromide cleavage of calponin, residues 2-51 were isolated. This fragment is shown to bind to CaBPs and the affinity for caltropin is slightly higher than that for calmodulin. A carboxyl-terminal truncated mutant of calponin comprising residues 1-228 (CP 1-228) has been produced by recombinant techniques. Analytical ultracentrifugation has shown that CP 1-228, like the parent calponin, is able to bind 2 mol of caltropin per mol of 1-228 in a Ca(2+)-dependent fashion, indicating that there is a second site of interaction between residues 52-228. Temperature denaturation of the carboxyl-terminal truncated fragment compared with whole calponin show that the carboxyl-terminal region does not change the temperature at which calponin melts; however, there is greater residual secondary structure with whole calponin versus the fragment. A second mutant produced through recombinant techniques comprises residues 45-228 and is also able to bind caltropin, thus mapping the location of the second site of interaction to near the actin binding site.
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PMID:Two domains of interaction with calcium binding proteins can be mapped using fragments of calponin. 775 87

Cajanus cajan lectin was isolated by ammonium sulfate fractionation and affinity chromatography on an IgM-Sepharose 6B column. Gel filtration and SDS-PAGE showed size homogeneity of the lectin. The lectin with M(r) 18,000 on SDS-PAGE had gel filtration behavior which was consistent with a molecular weight of 39 kDa and a Stokes radius of 2.74 nm. The results showed that the lectin is a dimer composed of identical subunits with N- and C-terminal residues of threonine and alanine, respectively. The glycoprotein lectin contained 3% concanavalin A-reactive neutral carbohydrates. Its amino acid composition is characterized by high contents of acidic amino acids. The number of tyrosine and tryptophan residues per mole of the lectin was determined to be 14 and 4, respectively, by spectrophotometry. Results on the effects of large numbers of saccharides on lectin-mediated hemagglutination and lectin-IgM precipitation showed that the C. cajan lectin was specific for mannose and glucose. A comparative study of the properties of C. cajan lectin and concanavalin A is also presented.
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PMID:Isolation and characterization of Cajanus cajan lectin. 778 24

A method for quantitation of tryptophan and tyrosine residues in proteins by fourth-derivative ultraviolet spectroscopy is described. The direct quantitation of tryptophan is based on measurement of a tryptophan-specific trough at 292 nm in the fourth derivative of a protein's ultraviolet absorption spectrum. A peak overlapping the tryptophan and tyrosine signatures at A282 is used to quantify tyrosine content. The procedure is accomplished by adding back known quantities of tyrosine to the sample and subtracting the contribution of tryptophan to the A282 peak to obtain an internal calibration curve. This curve is linear, with the ordinate axis intercept relating the quantity (residues/mole) of tyrosine present in the protein. This nondestructive and facile method was used to successfully predict the tryptophan and tyrosine content of a variety of well-characterized proteins. The utility of this method was further demonstrated by resolving the number of tryptophan and tyrosine residues in proteins oxidized by N-bromosuccinimide.
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PMID:Quantitation of tryptophan and tyrosine residues in proteins by fourth-derivative spectroscopy. 781 Aug 67

The rate of hydrolysis of phosphatidylcholine bilayers by soluble phospholipase A2 (PLA2) is greatly enhanced by the presence in the bilayer of a threshold mole fraction of the reaction products: fatty acid and lysophosphatidylcholine (lyso-PC). The threshold requirement of these products appears to vary as a function of vesicle and calcium concentration. To further identify the roles of myristic acid, lyso-PC, and calcium in promoting optimal PLA2 activity, we have quantified the various interactions among these components and dimyristoylphosphatidylcholine large unilamellar vesicles. The bilayer/water partition coefficient for myristic acid was obtained by competition of vesicles for the binding of the fatty acid to an acrylodan conjugate of an intestinal fatty acid binding protein as monitored by the acrylodan fluorescence emission spectrum. The partition coefficient for lyso-PC was obtained by a similar procedure using the tryptophan emission spectrum of bovine serum albumin. The effect of calcium concentration on these interactions was also quantified. These results were incorporated into an empirical model to describe the threshold requirements for these products in the bilayer. This information is vital for elucidating the mechanism of activation of PLA2 by the hydrolysis products.
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PMID:Quantification of the interactions among fatty acid, lysophosphatidylcholine, calcium, dimyristoylphosphatidylcholine vesicles, and phospholipase A2. 785 76


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