| 9169869 |
The nucleotide sequence of Saccharomyces cerevisiae chromosome VII. |
10.1002/(sici)1097-0061(19970915)13:11<1077::aid-yea152>3.0.co |
Nature |
The nucleotide sequence of Saccharomyces cerevisiae chromosome VII.
Abstract
- The complete nucleotide sequence of Saccharomyces cerevisiae chromosome VII has 572 predicted open reading frames (ORFs), of which 341 are new. No correlation was found between G+C content and gene density along the chromosome, and their variations are random. Of the ORFs, 17% show high similarity to human proteins. Almost half of the ORFs could be classified in functional categories, and there is a slight increase in the number of transcription (7.0%) and translation (5.2%) factors when compared with the complete S. cerevisiae genome. Accurate verification procedures demonstrate that there are less than two errors per 10,000 base pairs in the published sequence.
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| 9174364 |
Determinants involved in the affinity of alpha-conotoxins GI and SI for the muscle subtype of nicotinic acetylcholine receptors |
10.1021/bi970195w. |
Biochemistry |
Determinants involved in the affinity of alpha-conotoxins GI and SI for the muscle subtype of nicotinic acetylcholine receptors
Abstract
- Nicotinic acetylcholine receptors from muscle contain two functionally active and pharmacologically distinct acetylcholine-binding sites located at the alpha/gamma and alpha/delta subunit interfaces. The alpha-conotoxins are competitive antagonists of nicotinic receptors and can be highly site-selective, displaying greater than 10,000-fold differences in affinities for the two acetylcholine-binding sites on a single nicotinic receptor. The higher affinity site for alpha-conotoxins GI, MI, and SI is the alpha/delta site on mouse muscle-derived BC3H-1 receptors. However, alpha-conotoxins GI and MI exhibit higher affinity for the other site (alpha/gamma site) on nicotinic receptors from Torpedo californica electric organ. alpha-Conotoxin SI does not distinguish between the two acetylcholine-binding sites on Torpedo receptors. In this study, alpha-conotoxins [K10H]SI and [K10N]SI displayed wild-type affinity for the two acetylcholine-binding sites on BC3H-1 receptors but a 10-20-fold decrease in apparent affinity at one of the two acetylcholine-binding sites on Torpedo receptors. alpha-Conotoxin [P9K]SI displayed a selective and dramatic increase in the apparent affinity for the alpha/delta site of BC3H-1 receptors and for the alpha/gamma site of Torpedo receptors. alpha-Conotoxin [R9A]GI displayed a reduction in affinity for both acetylcholine-binding sites on BC3H-1 receptors, although the extent of its selectivity for the alpha/delta site was retained. alpha-Conotoxin [R9A]GI also displayed a loss of affinity for the two acetylcholine-binding sites on Torpedo receptors, but its site-selectivity was apparently abolished. These results indicate that positions 9 and 10 in alpha-conotoxins GI and SI are involved in complex species- and subunit-dependent interactions with nicotinic receptors.
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| 9175790 |
Identification of two novel insulin receptor mutations, Asp59Gly and Leu62Pro, in type A syndrome of extreme insulin resistance |
10.1006/bbrc.1997.6695. |
Biochem Biophys Res Commun |
Identification of two novel insulin receptor mutations, Asp59Gly and Leu62Pro, in type A syndrome of extreme insulin resistance
Abstract
- To elucidate genetic determinants of insulin resistance, we investigated insulin receptor (IR) and insulin receptor substrate-1 (IRS-1) genes, in vitro IR function and in vivo insulin sensitivity in a family with Type A syndrome. Two missense IR mutations (Asp59Gly and Leu62Pro) found in the proband, resulted in reduction by 90% of insulin binding to erythrocytes, decreased receptor autophosphorylation and a dramatic reduction of insulin sensitivity. The proband and mother were heterozygote for Gly972Arg IRS-1 variant. Asp59Gly mutation, also carried by proband's brother with no consequence on insulin sensitivity, was inherited from the mother who is diabetic and insulin resistant and Leu62Pro was from the father. We conclude that severity of insulin resistance in the proband may be explained by the genetic condition of compound heterozygote for IR mutations while severe insulin resistance in the mother raises the possibility that other genetic factors, like IRS-1 polymorphisms, may contribute to the phenotypic expression of IR mutations.
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| 9178760 |
Intracellular signaling of the Ufo/Axl receptor tyrosine kinase is mediated mainly by a multi-substrate docking-site |
10.1038/sj.onc.1201123. |
Oncogene |
Intracellular signaling of the Ufo/Axl receptor tyrosine kinase is mediated mainly by a multi-substrate docking-site
Abstract
- Ufo/Axl belongs to a new family of receptor tyrosine kinases with an extracellular structure similar to that of neural cell adhesion molecules. In order to elucidate intracellular signaling, the cytoplasmic moiety of Ufo/Axl was used to screen an expression library according to the CORT (cloning of receptor targets) method. Three putative Ufo substrates were identified: phospholipase Cgamma1 (PLCgamma), as well as p85alpha and p85beta subunits of phosphatidylinositol 3'-kinase (PI3-kinase). Subsequently, chimeric EGFR/Ufo receptors consisting of the extracellular domains of the epidermal growth factor receptor (EGFR) and the transmembrane and intracellular moiety of Ufo were engineered. Using different far-Western blot analyses and coimmunoprecipitation assays, receptor binding of PLCgamma and p85 proteins as well as GRB2, c-src and lck was examined in vitro and in vivo. Competitive inhibition of substrate binding and mutagenesis experiments with EGFR/Ufo constructs revealed C-terminal tyrosine 821 (EILpYVNMDEG) as a docking site for multiple effectors, namely PLCgamma, p85 proteins, GRB2, c-src and lck. Tyrosine 779 (DGLpYALMSRC) demonstrated an additional, but lower binding affinity for the p85 proteins in vitro. In addition, binding of PLCgamma occurred through tyrosine 866 (AGRpYVLCPST). Moreover, our in vivo data indicate that further direct or indirect binding sites for PLCgamma, GRB2, c-src and lck on the human Ufo receptor may exist.
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| 9179496 |
Construction and characterization of human brain cDNA libraries suitable for analysis of cDNA clones encoding relatively large proteins. |
10.1093/dnares/4.1.53 |
DNA Res. |
Construction and characterization of human brain cDNA libraries suitable for analysis of cDNA clones encoding relatively large proteins.
Abstract
- Analysis of proteins registered in the PIR protein database implied that most of relatively large proteins are related to important functions in higher multicellular organisms, but not many large proteins have been registered to date. To establish a protocol for efficient analysis of cDNA clones coding for large proteins, we constructed a series of strictly size-fractionated cDNA libraries of human brain, where the average insert sizes of cDNA clones ranged from 3.3 kb to 10 kb. As judged by hybridization analysis with probes derived from mRNAs of known sizes, the libraries with insert sizes up to 7 kb, at least, contained the clones corresponding to full-length transcripts in addition to truncated products of longer transcripts, but few chimeric clones. Using one of the fractionated libraries with an average insert size of 7 kb, the single-pass sequences from both the ends of randomly sampled clones were determined and sarched against DNA databases. Approximately 90% of the clones were found to be new with respect to their 5'-sequences while their 3'-sequences were frequently similar to the registered expression sequence tags. Examination of the protein-coding capacity in an in vitro transcription/translation system showed that about 20% of the clones direct the synthesis of proteins with apparent molecular masses larger than 50 kDa. The set of libraries constructed here should be very useful for the accumulation of sequence data on large proteins in the human brain.
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| 9195946 |
Cloning and characterization of a novel integrin beta3 subunit. |
10.1074/jbc.272.26.16390 |
J. Biol. Chem. |
Cloning and characterization of a novel integrin beta3 subunit.
Abstract
- We have identified a novel integrin beta3 subunit, termed beta3C, from a human osteoclast cDNA library. The COOH-terminal sequence and 3'-untranslated region of the beta3C subunit differs from the previously reported beta3A (platelet) and beta3B (placenta) sequences, while the regions coding for the transmembrane and extracellular domains are identical. The beta3C cytoplasmic domain contains 37 amino acids, the last 17 of which are encoded by a novel exon located about 6 kilobase pairs downstream of exon 14 of the beta3A gene. HEK 293 cells were stably co-transfected with alphaV and either beta3C (HEKbeta3C) or beta3A (HEKbeta3A). The viability of HEKbeta3C cells was lower than that of HEKbeta3A cells, and HEKbeta3C cells in culture grew as clusters rather than as a monolayer. The novel cytoplasmic domain did not affect receptor binding affinity; both alphaVbeta3A and alphaVbeta3C isoforms exhibited high affinity binding to 125I-echistatin and cyclic and linear RGD peptides. However, in contrast to HEKbeta3A, HEKbeta3C cells failed to adhere to osteopontin, an alphaVbeta3 matrix protein. The data provide further support for the key role of the cytoplasmic domain of the beta3 integrin in cell adhesion and suggest a potential role for the beta3C integrin subunit in modulating cell-matrix interactions.
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| 9199575 |
The Val985Met insulin-receptor variant in the Danish Caucasian population: lack of associations with non-insulin-dependent diabetes mellitus or insulin resistance |
10.1086/515464. |
Am J Hum Genet |
The Val985Met insulin-receptor variant in the Danish Caucasian population: lack of associations with non-insulin-dependent diabetes mellitus or insulin resistance
Abstract
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| 9202117 |
A peptide antibiotic from human skin |
10.1038/43088. |
Nature |
A peptide antibiotic from human skin
Abstract
|
| 9202395 |
Distribution of insulin/insulin-like growth factor-I hybrid receptors in human tissues. |
10.1016/s0303-7207(97)04050-1 |
Mol. Cell. Endocrinol. |
Distribution of insulin/insulin-like growth factor-I hybrid receptors in human tissues.
Abstract
- Insulin receptors (IR) and type 1 IGF receptors (IGF-IR) have been shown to form insulin/IGF-I hybrid receptors in tissues expressing both molecules. The biological function of hybrid receptors is still undefined. To date there is no information about the distribution of hybrid receptors in human tissues. We have applied two microwell-based immunoassays which are capable of quantitating hybrid receptors in small samples of human tissues and cells.
Results demonstrated that the proportion of total IGF-IR assembled as hybrids varied between 40 and 60%, thus indicating that hybrid receptors account for a large fraction of total IGF-I binding in human tissues. A significant fraction of total IR was assembled as hybrids in the tissues examined, varying from 37% in placenta to 45% in hepatoma, with the exception of adipose tissue where the fraction of insulin receptors forming hybrids was 17%. Because hybrid receptors bind IGF-I, but not insulin, with high affinity, it is likely that in human tissues hybrid receptors may be primarily activated by IGF-I rather than insulin under physiological conditions. Therefore, differences in hybrid receptors distribution may contribute to regulate tissue sensitivity to insulin and IGF-I by sequestering insulin receptor alphabeta-heterodimer in an IGF-I responsive form.
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| 9203163 |
Effects of arginine8, glycine-OH9-vasopressin on pentylenetetrazol seizures in mice. Interaction with adrenaline |
None |
Methods Find Exp Clin Pharmacol |
Effects of arginine8, glycine-OH9-vasopressin on pentylenetetrazol seizures in mice. Interaction with adrenaline
Abstract
- The effects of arginine8, glycine-OH9-vasopressin (AGV), alone and in combination with adrenaline, on pentylenetetrazol (PTZ) seizure threshold by timed intravenous infusion in tall vein and intensity by subcutaneous (s.c.) PTZ test (85 mg/kg) were studied in male albino mice. AGV was administered intracerebroventricularly (i.c.v.) at doses of 0.001, 0.01, 0.1, 1.0 and 5.0 ng/mouse 5, 15 and 30 min prior to PTZ AGV induced decrease of seizure threshold at middle doses (0.01 and 0.1) 5 and 15 min prior to PTZ (75 and 67% respectively vs. controls). Adrenaline (1 mg/kg, i.p.) potentiated the effect of AGV on seizure threshold. AGV also induced increase of seizure intensity at doses of 0.01 and 1.0 ng and decrease of latency of the first tonic seizure. Adrenaline (1.0 mg/kg, i.p.) enhanced the effects of AGV suggesting interactions of vasopressin with adrenergic neurotransmission in the CNS.
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| 9214615 |
The thrombin E192Q-BPTI complex reveals gross structural rearrangements: implications for the interaction with antithrombin and thrombomodulin |
10.1093/emboj/16.11.2977. |
EMBO J |
The thrombin E192Q-BPTI complex reveals gross structural rearrangements: implications for the interaction with antithrombin and thrombomodulin
Abstract
- Previous crystal structures of thrombin indicate that the 60-insertion loop is a rigid moiety that partially occludes the active site, suggesting that this structural feature plays a decisive role in restricting thrombin's specificity. This restricted specificity is typified by the experimental observation that thrombin is not inhibited by micromolar concentrations of basic pancreatic trypsin inhibitor (BPTI). Surprisingly, a single atom mutation in thrombin (E192Q) results in a 10(-8) M affinity for BPTI. The crystal structure of human thrombin mutant E192Q has been solved in complex with BPTI at 2.3 A resolution. Binding of the Kunitz inhibitor is accompanied by gross structural rearrangements in thrombin. In particular, thrombin's 60-loop is found in a significantly different conformation. Concomitant reorganization of other surface loops that surround the active site, i.e. the 37-loop, the 148-loop and the 99-loop, is observed. Thrombin can therefore undergo major structural reorganization upon strong ligand binding. Implications for the interaction of thrombin with antithrombin and thrombomodulin are discussed.
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| 9214759 |
Primary structure of 6.5k-arginine/glutamate-rich polypeptide from the seeds of sponge gourd (Luffa cylindrica) |
10.1271/bbb.61.984. |
Biosci Biotechnol Biochem |
Primary structure of 6.5k-arginine/glutamate-rich polypeptide from the seeds of sponge gourd (Luffa cylindrica)
Abstract
- The amino acid sequence of 6.5k-arginine/glutamate rich polypeptide (6.5k-AGRP) from the seeds of sponge gourd (Luffa cylindrica) has been determined. The 6.5k-AGRP consists of a 47-residue polypeptide chain containing two disulfide bonds, and a molecular mass calculated to be 5695 Da, which fully coincides with a value of M+H+ = m/zeta 5693.39 obtained by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). The mass spectrometric evidence indicated that 6.5k-AGRP is also present partially truncated at the C-terminus. In our preparations, approximately half of the polypeptide molecules have the C-terminal sequence Arg-Arg-Glu-Val-Asp; the other half lack Val-Asp and end with the glutamic acid, making a total of 45 residues in the polypeptide chain. The two disulfide bonds connect Cys12 to Cys33 and Cys16 to Cys29. Comparison of the amino acid sequence of 6.5k-AGRP with those of the other known proteins included in the PIR protein sequence database showed that it is related to the amino acid sequence of the N-terminal region encoded by the first exon of the cocoa (Theobroma cacao) and cotton seeds vicilin genes, sharing a characteristic two Cys-Xaa-Xaa-Xaa-Cys motif.
|
| 9215749 |
Hematologically important mutations: Glanzmann thrombasthenia |
10.1006/bcmd.1997.0117. |
Blood Cells Mol Dis |
Hematologically important mutations: Glanzmann thrombasthenia
Abstract
|
| 9225241 |
Elucidation of the structure of constrained bicyclopeptides in solution by two-dimensional cross-relaxation spectroscopy: amatoxin analogues |
10.1002/psc.44. |
J Pept Sci |
Elucidation of the structure of constrained bicyclopeptides in solution by two-dimensional cross-relaxation spectroscopy: amatoxin analogues
Abstract
- The evaluation of peptide structures in solution is made feasible by the combined use of two-dimensional NMR in the laboratory (NOESY) and rotating frames (ROESY), and by the use of molecular dynamics calculations. The present paper describes how both the NMR method and molecular dynamics calculations were applied to very rigid synthetic bicycle peptides that are analogues of natural amatoxins. The NMR theory, which allows the estimate of interatomic distances between interacting nuclei, is briefly discussed. The experimental data were compared with those of known solid-state structures. Three amatoxin analogues have been examined. Of these, one is biologically active (S-deoxo gammaR OH-Ile3-amaninamide) and its structure in the solid state has recently been worked out. The second and third analogues (S-dexo-Ile3-Ala5-amaninamide and S-deoxo-D-Ile3-amaninamide, respectively) are inactive and their solid-state structures are unknown. The data presented confirm the authors previous hypothesis that lack of biological activity of S-deoxo-Ile3-Ala5-amaninamide is due to the masking of the tryptophan ring by the methyl group of L-Ala and not to massive conformational changes of the analogue.
|
| 9230480 |
Lipopeptides with improved properties: structure by NMR, purification by HPLC and structure-activity relationships of new isoleucyl-rich surfactins |
10.1002/(sici)1099-1387(199703)3:2<145::aid-psc96>3.0.co;2-y. |
J Pept Sci |
Lipopeptides with improved properties: structure by NMR, purification by HPLC and structure-activity relationships of new isoleucyl-rich surfactins
Abstract
- The biosynthesis of bacterial isoleucyl-rich surfactins was controlled by supplementation of L-isoleucine to the culture medium. Two new variants, the Ile4,7- and Ile2,4,7surfactins, were thus produced by Bacillus subtilis and their separation was achieved by reverse-phase HPLC. Amino acids of the heptapeptide moiety were analysed by chemical methods, and the lipid moiety was identified by beta-hydroxy anteiso pentadecanoic acid by combined GC/MS. Sequences were established on the basis of two-dimensional NMR data. Because conformational parameters issuing from NMR spectra suggested that the cyclic backbone fold was globally conserved in the new variants, structure-activity relationships were discussed in details on the basis of the three-dimensional model of surfactin in solution. Indeed, both variants have increased surface properties compared with that of surfactin, and this improvement is assigned to an increase of the hydrophobicity of the apolar domain favouring micellization. Furthermore, the additional Leu-to-Ile substitution at position 2 in the Ile2,4,7surfactin leads to a substantial increase of its affinity for calcium, when compared with that of Ile4,7surfactin or surfactin. This effect is assigned, from the model, to an increase in the accessibility of the acidic side chains constituting the calcium binding site. Thus, the propensities of such active lipopeptides for both hydrophobic and electrostatic interactions were improved, further substantiating that they can be rationally designed.
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