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)

The expression of MUC1, Tn (GalNAc alpha 1-O-Ser/Thr) and sialosyl Tn (STn) (NeuAc alpha 2,6 GalNAc alpha 1-O-Ser/Thr) antigens, which are useful markers for the prognosis of cancer in other organs, was examined immunohistochemically in a series of 45 eyelid tumors and 5 pseudotumors: basal cell carcinoma, 18; squamous cell carcinoma, 11; sebaceous gland carcinoma, 6; seborrheic keratosis, 4; papilloma, 3; verruca vulgaris, 2; nevus, 1; and granuloma, 5. The MUC1 antigen was identified in all squamous cell and sebaceous gland carcinomas, but not in basal cell carcinoma or the benign tumors. The Tn antigen was expressed in all the sebaceous gland, half of the squamous cell, and only rarely in the basal cell carcinomas. The STn antigen was expressed in all seborrheic keratosis and in the majority of squamous cell carcinomas, but only rarely in sebaceous gland and basal cell carcinomas. Eyelid tumors are frequently associated with apomucin and mucin-carbohydrate antigens: the MUC1 glycoprotein appears to be related to the malignant potential of eyelid tumors, and may be a useful marker for the differential diagnosis of invasive tumors, including sebaceous gland and squamous cell carcinomas.
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PMID:Glycopathological study of eyelid tumors and pseudotumors. 950 2

Electron spin-echo envelope modulation (ESEEM) spectroscopy is widely used to investigate the active sites of biological molecules in frozen solutions. Various cryoprotection techniques, particularly the addition of co-solvents, are commonly employed in the preparation of such samples. In conjunction with ESEEM studies of Mn(II) guanosine nucleotide complexes of p21 ras, we have investigated the effects of cryoprotection on the spectroscopy, the structure, and the activity of this protein. Echo decay times, which typically govern ESEEM spectral resolution, were found to vary linearly with the concentration of glycerol or methyl alpha-D-glucopyranoside (MG), with both additives equally effective on a per-mole basis. The effect of glycerol and MG on the ESEEM amplitudes of various protein nucleiwas studied in ras p21.Mn(II). 5'guanylylimido-diphosphate(p21.Mn(II)-GMPPNP) complexes: these additives did not alter the distances of these nuclei from the Mn(II) ion. In particular, in p21 incorporating [2H-3]Thr, the Mn(II)-[2H-3]Thr35 distance was found to be unaffected by the concentration of cryoprotectant or the rate of freezing. The proximity of the cryoprotectants to the Mn(II) ion was probed by 2H ESEEM in solutions made with d5-glycerol and d7-methyl alpha-D-glucopyranoside (d7-MG). In p21.Mn(II)GMPPNP, the large deuterium modulations from the d5-glycerol exhibit saturation behavior with increasing d5-glycerol concentration, implying that glycerol, a widely used cryoprotectant, replaces the aquo ligands of the Mn(II) ion. The interaction between the Mn(II) ion of p21 and MG, however, is less intimate: the deuterium ESEEM amplitudes are much smaller for samples prepared with d7-MG than with d5-glycerol. Several polyhydroxylic compounds were found to have essentially no effect on the ability of the guanosine 5'-triphosphate (GTP) hydrolysis activating protein, GAP334, to catalyze hydrolysis of p21. guanosine 5'-triphosphate. This observation implies that the introduction of cryoprotectant does not significantly perturb the structure of p21 and gives insight into the mechanism of the GTPase reaction.
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PMID:The effects of cryoprotection on the structure and activity of p21 ras: implications for electron spin-echo envelope modulation spectroscopy. 974 Jul 40

We obtained evidence that Rho-associated kinase (Rho-kinase) phosphorylates desmin, the myogenic intermediate filament protein, with approximately 2 mol phosphate per mole of desmin in vitro. Desmin phosphorylated by Rho-kinase lost the potential to form 10-nm filaments. Thr-16, Thr-75, and Thr-76 on desmin proved to be the major phosphorylation sites for Rho-kinase. All these sites are located within the head domain and are different from the reported phosphorylation sites of protein kinase. A, protein kinase C, and cdc2 kinase. We are entertaining the notion that Rho-kinase may regulate filament structures of desmin by site-specific phosphorylation.
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PMID:Rho-associated kinase phosphorylates desmin, the myogenic intermediate filament protein, at unique amino-terminal sites. 987 13

Inhibitor 1 (I-1) is a protein inhibitor of protein phosphatase 1 (PP1), a major eukaryotic Ser/Thr phosphatase. Nonphosphorylated I-1 is inactive, whereas phosphorylated I-1 is a potent PP1 inhibitor. I-1 is phosphorylated in vivo on Thr(35) and Ser(67). Thr(35) is phosphorylated by cAMP-dependent protein kinase (A kinase), and Thr(35)-phosphorylated I-1 inhibits PP1. Until now the kinase that phosphorylates Ser(67) had not been identified and the physiological role of Ser(67) phosphorylation was unknown. In this study we detected a high level of kinase activity in brain extract when a glutathione S-transferase (GST) fusion I-1 mutant containing an Ala substituted for Thr(35) [GST-I-1(T35A)] was used as the substrate. GST-I-1(T35A) kinase and neuronal cdc2-like protein kinase (NCLK) in the brain extract could not be separated from each other by a series of sequential chromatographies. GST-I-1(T35A) kinase immunoprecipitated with anti-NCLK antibody from kinase-active column fractions. Purified NCLK-phosphorylated GST-I-1(T35A) and I-1 (0.7 mole of phosphate per mole of I-1). HPLC phosphopeptide mapping, amino acid sequencing, and site-directed mutagenesis determined that NCLK phosphorylates Ser(67) of I-1. NCLK-phosphorylated I-1 and I-1(T35A) inhibited PP1 with IC(50) values approximately 9.5 and 13. 8 nM, respectively. When compared, A kinase-phosphorylated I-1 was only approximately 1.2 times more inhibitory than NCLK-phosphorylated I-1. Our data indicate that NCLK is a potential in vivo I-1 kinase and that Thr(35) and Ser(67) phosphorylation independently activate I-1.
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PMID:Ser67-phosphorylated inhibitor 1 is a potent protein phosphatase 1 inhibitor. 1081 8

The N-terminal SH3 domain of the Drosophila drk protein (drkN SH3) exists in equilibrium between folded and unfolded states under non-denaturing buffer conditions. In order to examine the origins of this instability, we have made mutations in the domain and characterized the thermodynamics and kinetics of folding. Results of substitutions of negatively charged residues to neutral amino acid residues suggest that the large electrostatic potential of the domain does not play a dominant role in the instability of the domain. Sequence alignment of a large number of SH3 domains reveals that the drkN SH3 domain has a threonine (T22) at a position corresponding to an otherwise highly conserved glycine residue in the diverging beta-turn connecting the beta3 and beta4 strands. Mutation of T22 to glycine results in significant stabilization of the drkN SH3 domain by 2.5 kcal/mole. To further characterize the basis for the stabilization of the T22 mutant relative to wild-type, we made additional mutant proteins with substitutions of residue T22. A strong correlation is seen between protein stability or folding rate and propensity for native beta-turn structure at this position. Correlation of folding rates with AGADIR predictions of non-native helical structure in the diverging turn region, along with our previous NMR evidence for non-native structure in this region of the unfolded state of the drkN SH3 domain, suggests that the free energy of the unfolded state also plays a role in stability. This result highlights the importance of both folded and unfolded states for understanding protein stability.
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PMID:Dramatic stabilization of an SH3 domain by a single substitution: roles of the folded and unfolded states. 1127 10

Artery wall binding peptide (AWBP; Cys-Gly-Arg-Ala-Leu-Val-Asp-Thr-Leu-Lys-Phe-Val-Thr-Gln-Ala-Glu-Gly-Ala-Lys), a specific targeting peptide, was conjugated to poly(ethylene glycol)-grafted-poly(L-lysine) (PEG-g-PLL) to enhance the gene transfer to artery wall cells. AWBP-PEG-PLL was synthesized by the reaction between the vinylsulfone group of PEG-g-PLL and the thiol group of cysteine in AWBP. 1H-NMR analysis confirmed the composition of the obtained polymer and indicated that four mol of AWBP were reacted to one mole of VS-PEG-PLL. The particles of AWBP-PEG-PLL/pDNA complexes were determined spherical with a size of approximately 100 nm by dynamic light scattering (DLS) and atomic force microscopy (AFM). Agarose gel retardation assay indicated that AWBP-PEG-PLL was able to condense plasmid DNA and reach complete complexation at and above a charge ratio 1/1 (+/-). Transfection efficiency of AWBP-PEG-PLL/pDNA complexes was 150-180 times higher than that of control systems, such as PEG-g-PLL/pDNA and PLL/pDNA, in both bovine aorta endothelial cells and smooth muscle cells. Luciferase activities of AWBP-PEG-PLL depended on the amount of free AWBP, while those of the control carriers such as PLL and PEG-g-PLL were not affected by free AWBP. These results supported that gene transfer of AWBP-PEG-PLL/pDNA complexes to bovine aorta wall cells was mediated by specific artery wall cell receptor-mediated endocytosis.
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PMID:Artery wall binding peptide-poly(ethylene glycol)-grafted-poly(L-lysine)-based gene delivery to artery wall cells. 1177 68

In this study, we have analyzed experimentally the helical intrinsic propensities of non-charged and non-aromatic residues at different C-terminal positions (C1, C2, C3) of an Ala-based peptide. The effect was found to be complex, resulting in extra stabilization or destabilization, depending on guest amino acid and position under consideration. Polar (Ser, Thr, Cys, Asn, and Gln) amino acids and Gly were found to have significantly larger helical propensities at several C-terminal positions compared with the alpha-helix center (-1.0 kcal/mole in some cases). Some of the nonpolar residues, especially beta-branched ones (Val and Ile) are significantly more favorable at position C3 (-0.3 to -0.4 kcal/mole), although having minor differences at other C-terminal positions compared with the alpha-helix center. Leu has moderate (-0.1 to -0.2 kcal/mole) stabilization effects at position C2 and C3, whereas being relatively neutral at C1. Finally, Met was found to be unfavorable at C1 and C2 ( +0.2 kcal/mole) and favorable at C3 (-0.2 kcal/mole). Thus, significant differences found between the intrinsic helical propensities at the C-terminal positions and those in the alpha-helix center must be accounted for in helix/coil transition theories and in protein design.
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PMID:Amino acid intrinsic alpha-helical propensities III: positional dependence at several positions of C terminus. 1191 21

A major goal of this paper was to estimate a dynamic range of equilibrium constant for the opening of a single peptide bond in a model protein, bovine pancreatic trypsin inhibitor (BPTI). Ten mutants of BPTI containing a single Xaa-->Met substitution introduced in different parts of the molecule were expressed in Escherichia coli. The mutants were folded, purified to homogeneity, and cleaved with cyanogen bromide to respective cleaved forms. Conformation of the intact mutants was similar to the wildtype, as judged from their circular dichroism spectra. Substantial conformational changes were observed on the chemical cleavage of three single peptide bonds--Met46-Ser, Met49-Cys, and Met53-Thr--located within the C-terminal helix. Cleavage of those peptide bonds caused a significant destabilization of the molecule, with a drop of the denaturation temperature by 56.4 degrees C to 68 degrees C at pH 4.3. Opening of the remaining seven peptide bonds was related to a 10.8 degrees C to 39.4 degrees C decrease in T(den). Free energies of the opening of 10 single peptide bonds in native mutants (Delta G(op,N)) were estimated from the thermodynamic cycle that links denaturation and cleavage free energies. To calculate those values, we assumed that the free energy of opening of a single peptide bond in the denatured state (Delta G(op,D)) was equal to -2.7 kcal/mole, as reported previously. Calculated Delta G(op,N) values in BPTI were in the range from 0.2 to 10 kcal/mole, which was equivalent to a >1 million-fold difference in equilibrium constants. The values of Delta G(op,N) were the largest for peptide bonds located in the C-terminal helix and significantly lower for peptide bonds in the beta-structure or loop regions. It appears that opening constants for single peptide bonds in various proteins span across 33 orders of magnitude. Typical equilibrium values for a single peptide bond opening in a protein containing secondary structure elements fall into negligibly low values, from 10(-3) to 10(-8), and are efficient to ensure stability against proteolysis.
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PMID:Thermodynamics of single peptide bond cleavage in bovine pancreatic trypsin inhibitor (BPTI). 1191 35

A comparative study was performed on lysozyme modification after exposure to Fenton reagent (Fe(II)/H2 O2) or hydroxyl radicals produced by y radiation. The conditions were adjusted to obtain, with both systems, a 50% loss of activity of the modified ensemble. Gamma radiation modified almost all types of amino acid residues in the enzyme, with little specificity. The modification order was Tyr > Met = Cys > Lys > Ile + Leu > Gly > Pro = Phe > Thr + Ala > Trp = Ser > Arg > Asp + Glu, with 42 mol of modified residues per initial mole of native enzyme. In contrast, when the enzyme was exposed to the Fenton reaction, only some types of amino acids were modified. Furthermore, a smaller number of residues (13.5) were damaged per initial mole of enzyme. The order of the modified residues was Tyr > Cys > Trp > Met His > Ile + Leu > Val > Arg. These results demonstrate that the modifications elicited by these two free radical sources follow different mechanisms. An intramolecular free radical chain reaction is proposed to play a dominant role in the oxidative modification of the protein promoted by gamma radiation.
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PMID:Lysozyme modification by the fenton reaction and gamma radiation. 1207 46

Aquaporins (AQP) were originally regarded as plasma membrane channels that are freely permeated by water or small uncharged solutes but not by ions. Unlike other aquaporins, AQP6 overexpressed in Xenopus laevis oocytes was previously found to exhibit Hg2+ or pH-activated ion conductance. AQP6 could not be analyzed electrophysiologically in mammalian cells, however, because the protein is restricted to intracellular vesicles. Here we report that addition of a green fluorescence protein (GFP) tag to the N terminus of rat AQP6 (GFP-AQP6) redirects the protein to the plasma membranes of transfected mammalian cells. This permitted measurement of rapid, reversible, pH-induced anion currents by GFP-AQP6 in human embryonic kidney 293 cells. Surprisingly, anion selectivity relative to Cl- revealed high nitrate permeability even at pH 7.4; P(NO3)/P(Cl) > 9.8. Site-directed mutation of a pore-lining threonine to isoleucine at position 63 at the midpoint of the channel reduced NO3-/Cl- selectivity. Moreover, no anomalous mole-fraction behavior was observed with NO3-/Cl- mixtures, suggesting a single ion-binding pore in each subunit. Our studies indicate that AQP6 exhibits a new form of anion permeation with marked specificity for nitrate conferred by a specific pore-lining residue, observations that imply that the primary role of AQP6 may be in cellular regulation rather than simple fluid transport.
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PMID:Characterization of aquaporin-6 as a nitrate channel in mammalian cells. Requirement of pore-lining residue threonine 63. 1217 1


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