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)

Toxin A and B, the major virulence factors of Clostridium difficile, are the causative agents of antibiotic-associated pseudomembranous colitis. In cultured cell lines their potent cytotoxicity results from their ability to induce disaggregation of the microfilament cytoskeleton. Toxin B acts on the low-molecular-mass GTPase RhoA, which is involved in the regulation of the actin cytoskeleton. We report here that toxin B catalyses the incorporation of up to one mole of glucose per mole of RhoA at the amino acid threonine at position 37. The modification was identified and localized by tandem electrospray mass spectrometry. UDP-glucose selectively serves as cosubstrate for the monoglucosylation reaction catalysed by toxin B. Microinjection of RhoA previously glucosylated by toxin B into monolayer cells caused disaggregation of actin filaments, indicating a dominant-negative activity of glucosylated RhoA.
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PMID:Glucosylation of Rho proteins by Clostridium difficile toxin B. 777 59

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

Lipoprotein(a) [Lp(a)], a variant of low-density lipoprotein, is heterogeneous in density because of variability in the content and composition of its core lipids and size polymorphism of its specific glycoprotein component, apolipoprotein(a) [apo(a)]. In some individuals, density polymorphism may also derive from the fact that Lp(a) contains 2 mol of apo(a) per mole of apoB100, contrary to the more common 1:1 molar stoichiometry. Moreover, the size of apo(a) is polymorphic because of variations in the number of kringle 4 type 2 repeats. Another type of apo(a) polymorphism is related to sequence mutations at the kringle level. Two mutations can occur in kringle 4 type 10: one, Trp72-->Arg, is affiliated with an Lp(a) that is lysine-binding defective; the other, Met66-->Thr, with a normal lysine-binding function. Thus, Lp(a) is structurally and functionally polymorphic, a notion that must be considered in assessing the cardiovascular pathogenicity of this lipoprotein variant and in immunoquantification assays.
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PMID:Structural and functional polymorphism of lipoprotein(a): biological and clinical implications. 781 75

The complete carbohydrate structure of the asparagine-linked oligosaccharides of rat plasma thiostatin was elucidated through chemical and enzymatic methods including gas chromatography-mass spectrometry (GC-MS) and lectin affinity chromatography. Pronase digestion of thiostatin yielded a major glycopeptide fraction with asparagine the most abundant amino acid present. Based on one mole of aspartic acid, the following molar ratios obtained for the four major amino acids: aspartic acid (1.0), threonine (0.53), glycine (0.48) and serine (0.30). Neutral sugar analysis yielded a 3:2 molar ratio for mannose to galactose based on an assigned value to mannose of 3. On this basis, the fraction also contained 3 residues of sialic acid and, on average, 0 to 1 residue of fucose. GC-MS of partially methylated alditol acetates from the glycopeptide fraction identified the presence of biantennary and triantennary structure. Analyses of the neutral sugar and amino-acid composition, together with methylation data, support a biantennary N-linked structure for this major glycopeptide fraction and a triantennary N-linked structure as a lesser component. Sequencing of the desialyated 14C-labelled glycopeptide fraction by sequential exoglycosidase digestion and lectin affinity chromatography uncovered the following saccharide order: terminal galactose, N-acetylglucosamine and pentasaccharide inner core. This sequence is consistent with the N-linked glycan structures demonstrated by methylation and compositional analyses.
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PMID:The carbohydrate structure of the asparagine-linked oligosaccharides of rat plasma thiostatin. 794 64

The 7-ethoxycoumarin O-deethylase activity of rat liver cytochrome P450 2B1 reconstituted with NADPH-cytochrome P450 reductase and lipid was inactivated by 2-ethynylnaphthalene (2EN) in a time- and NADPH-dependent manner, and the loss of activity followed pseudo-first-order kinetics. The extrapolated KI and kinactivation were 0.08 microM and 0.83 min-1, respectively. The loss of 7-ethoxycoumarin O-deethylation activity displayed a number of characteristics consistent with mechanism-based inactivation, including irreversibility, saturability, protection by an alternate substrate, and the lack of an effect of exogenous nucleophiles on the inactivation. The inactivation was not accompanied by a concomitant loss of spectrally detectable cytochrome P450. HPLC analysis showed that [3H]2EN was irreversibly bound to the protein moiety of cytochrome P450 and the stoichiometry of inactivation was approximately 1.3 mol of 2EN bound per mole of cytochrome P450. Liquid chromatographic and GC-MS analyses of the organic extracts from these incubations showed that the major metabolite was 2-naphthylacetic acid, and a partition ratio of 4-5 mol of acid produced per mole of cytochrome P450 2B1 inactivated was determined. A radiolabeled peptide, approximately 6.5 kDa when analyzed by Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), was isolated by HPLC from a tryptic digest of the [3H]2EN-inactivated cytochrome P450 and NADPH-cytochrome P450 reductase. Sequence data were obtained after cyanogen bromide cleavage of this amino-terminally blocked peptide. These results in conjunction with the results from the cleavage of the intact [3H]2EN-inactivated cytochrome P450 by cyanogen bromide and separation of the peptides either by HPLC or by Tricine-SDS-PAGE followed by transfer of the peptides to a poly(vinylidene difluoride) membrane and sequencing of the labeled peptides from both experiments, led to the identification of a 2EN-modified active-site peptide with the sequence ISLLSLFFAGTETSSTTLRYGFLLM. This corresponds to positions 290-314 in cytochrome P450 2B1. Sequence alignments of cytochrome P450 2B1 with cytochrome P450 2B1 with cytochrome P450 101 predict that this region might correspond to helix I of the bacterial protein [Poulos, T.L. (1988) Pharm. Res. 5, 67-75] that contains a highly conserved threonine residue involved in oxygen binding.
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PMID:Mechanism-based inactivation of cytochrome P450 2B1 by 2-ethynylnaphthalene: identification of an active-site peptide. 837 44

The function of the uterine smooth muscle in gestation and parturition is affected by a variety of hormones and biomolecules, some of which alter the intracellular levels of cAMP and Ca2+. Since the activity of smooth muscle MLCK has been shown to be modulated by phosphorylation, the effect of this modification of pregnant sheep myometrium (psm) MLCK by the catalytic subunit of cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) was studied. In contrast to other smooth muscle MLCK reported, PKA incorporates 2.0-2.2 moles phosphate into a mole of psm MLCK both in the presence and absence of Ca(2+)-calmodulin. Modification of serine residues inhibited the activity of the enzyme. PKC also incorporated 2.0-2.1 moles of phosphate per mole psmMLCK under both conditions but had no effect on the MLCK activity. Sequential phosphorylation by PKC and PKA incorporated 3.8-4.1 moles phosphate suggesting that the amino acid residues modified by the two kinases are different. Phosphoamino acid analysis of the MLCK revealed that PKC phosphorylated serine and threonine residues. The double reciprocal plots of the enzyme activity and calmodulin concentrations showed that the Vmax of the reaction is not altered by phosphorylation by PKA but the calmodulin concentration require for half-maximal activation is increased about 4-fold. Only 10 out of 17 monoclonal antibodies to various regions of the turkey gizzard MLCK cross-reacted with psmMLCK suggesting structural differences between these enzymes. Comparison of the deduced amino acid sequence of the cDNA encoding the C-terminal half of the psmMLCK molecule showed that while cgMLCK and psmMLCK are highly homologous, a number of nonconservative substitutions are present, particularly near the PKA phosphorylation site B (S828).
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PMID:Phosphorylation and partial sequence of pregnant sheep myometrium myosin light chain kinase. 856 50

Individual variability in circadian locomotor activity has recently discovered in the blind mole rat, Spalax ehrenbergi. An interesting association was found between different circadian types and two DNA fragments, 5.6 and 5.9 kb long, that contain the ACNGGN repeat sequence, homologous to a part of the period gene of Drosophila. Nine of 12 arrythmic animals showed the 5.6-kb band, while 13 of 17 circadian rhythmic animals had the 5.9-kb band. This repeat exists also in the brain RNA of the mole rat, apparently in higher quantities during the sleeping phase, suggesting that an unusual protein(s), composed of a poly-Thr-Gly segment, affects in circadian rhythm.
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PMID:Circadian rhythm and the per ACNGGN repeat in the mole rat, Spalax ehrenbergi. 863 53

Cathepsin H (EC 3.4.22.16) from cow brain, purified to approximately 1800-fold with approximately 26% activity yield, hydrolysed BANA, Leu-2-NNap, Arg-2-NNap, and Met-2-NNap maximally at pH 6.5, 6.8, 7.0 and 7.2, respectively. It was activated by sulphydryl compounds and EDTA while sulphydryl alkylators and blockers were found to inhibit the enzyme activity. Met-2-NNap was found to be the best substrate followed by Thr-2-NNap, His-2-NNap, Leu-2-NNap, Arg-2-NNap and Ala-2-NNap, respectively. The Km values for hydrolysis of various substrates viz., Met-2-NNap, Leu-2-NNap, Arg-2-NNap, Arg-NNapOMe, Thr-2-NNap, His-2-NNap, BANA, Arg-pNA and Lys-pNA were 0.128, 0.167, 0.169, 0.288, 0.428, 0.500, 0.667, 0.195 and 0.476 mM, respectively. The temperature optima for hydrolysis of BANA and Leu-2-NNap were approximately 45 degrees C and approximately 50 degrees C with activation energies of approximately 13.7 and approximately 11.0 kcal mole-1, respectively. The enzyme was fairly stable upto 50 degrees C and between pH 4.0-7.5.
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PMID:Physico-chemical properties of brain cathepsin H. 871 50

The effect of L-TYR on rat uterine cytosol estradiol and progesterone receptor contents was studied. The rats were divided into 4 groups: proestrus, estrus, metestrus and diestrus. One horn of each uterus was injected with L-TYR (2 mmol/L, 0.1 ml), while the other with 0.1 ml 0.9% NaCl serving as control. The mole concentration of receptor was calculated with RRA and cytosol receptor content was expressed as fmol/mg protein. It was shown that L-TYR decreased significantly the uterine estradiol and progesterone receptors in proestrus, estrus and diestrus phases of the estrus cycle, but without effect on metestrus. This was most probably due to competitive combination of TYR with some functional groups of the estradiol receptor because of similar chemical conformation of TYR to estradiol. Threonine could also decrease, to some extent, the uterine cytosol progesterone receptor content at estrus and dioestrus phases. Serine had no effect on the contents of uterine cytosol either estradiol or progesterone receptor in normal and ovariectomized rats. The present observation indicates that L-TYR appears to affect the synthesis of the cytosol estradiol and progesterone receptor in the rat uterus independent, however, of endogenous ovarian sex hormones, since the effect is still present in the ovariectomized animals.
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PMID:[Effect of L-TYR on the uterine cytosol estradiol and progesterone receptors in rat]. 875 96

Myosin II heavy chain (MHC)-specific protein kinase C (MHC-PKC) isolated from the ameba, Dictyostelium discoideum, regulates myosin II assembly and localization in response to the chemoattractant cAMP. cAMP stimulation of Dictyostelium cells leads to translocation of MHC-PKC from the cytosol to the membrane fraction, as well as causing an increase in both MHC-PKC phosphorylation and its kinase activity. MHC-PKC undergoes autophosphorylation with each mole of kinase incorporating about 20 mol of phosphate. The MHC-PKC autophosphorylation sites are thought to be located within a domain at the COOH-terminal region of MHC-PKC that contains a cluster of 21 serine and threonine residues. Here we report that deletion of this domain abolished the ability of the enzyme to undergo autophosphorylation in vitro. Furthermore, after this deletion, cAMP-dependent autophosphorylation of MHC-PKC as well as cAMP-dependent increases in kinase activity and subcellular localization were also abolished. These results provide evidence for the role of autophosphorylation in the regulation of MHC-PKC and indicate that this MHC-PKC autophosphorylation is required for the kinase activation in response to cAMP and for subcellular localization.
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PMID:Autophosphorylation of Dictyostelium myosin II heavy chain-specific protein kinase C is required for its activation and membrane dissociation. 899 70


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