| 7694683 |
Amino acid 489 is encoded by a mutational "hot spot" on the beta 3 integrin chain: the CA/TU human platelet alloantigen system |
None |
Blood |
Amino acid 489 is encoded by a mutational "hot spot" on the beta 3 integrin chain: the CA/TU human platelet alloantigen system
Abstract
- A new platelet alloantigen, termed CA, has recently been implicated in a case of neonatal alloimmune thrombocytopenia (NATP) in a Filipino family in Canada. Maternal anti-CA serum reacted with glycoprotein (GP) IIIa and maintained its reactivity after removal of high mannose carbohydrate residues from GPIIIa. The monoclonal antibody (MoAb) AP3 partially blocked binding of anti-CA to GPIIIa, suggesting that the CA polymorphism is proximal to the AP3 epitope. Platelet RNA polymerase chain reaction (PCR) was used to amplify the region of GPIIIa cDNA that encodes this region of the protein. DNA sequence analysis showed a G<==>A nucleotide substitution at base 1564 that results in an arginine (Arg) (CGG)<==>glutamine (Gln) (CAG) polymorphism in amino acid (AA) 489. Further analysis of PCR-amplified genomic DNA from 27 normal individuals showed that AA 489 is encoded by a mutational "hot spot" of the GPIIIa gene, as three different codons for the wild-type Arg489 of GPIIIa were also found. The codon usage for Arg489 was found to be: CGG (63%), CGA (37%), and CGC (< 1%). These frequency data were valuable in determining the relationship of the CA alloantigen to the serologically defined TU GPIIIa polymorphism that is present in low frequency in the Finish population. Analyses of PCR-amplified genomic DNA showed the CA and TU alloantigens to be identical at the molecular level. Definition of these new molecular variants of the beta 3 integrin chain should prove valuable in the diagnosis of NATP in these two geographically disparate populations, and it may also provide useful genetic markers for examining other pathologic variations of the GPIIb-IIIa complex.
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| 7696625 |
ETB receptor involvement in stimulatory and neurotoxic action of endothelin on dopamine neurones |
10.1097/00001756-199412000-00062. |
Neuroreport |
ETB receptor involvement in stimulatory and neurotoxic action of endothelin on dopamine neurones
Abstract
- We examined the role of endothelin (ET) receptor subtypes in mediating the transient and sustained release of dopamine (DA) evoked by ETs and ET-1-induced dopaminergic dysfunction in rat striatal slices. Both phases of the release of DA evoked by ET-1 and ET-3 were inhibited by RES-701-1 (ETB antagonist) but not BQ-123 (ETA antagonist). The high K(+)-evoked DA release from slices remained impaired following a brief exposure to ET-1, under conditions of hypoxia/hypoglycaemia. RES-701-1 but not BQ-123 led to a recovery from ET-1-induced striatal dysfunction. Therefore, ETB receptors are involved in the stimulatory and neurotoxic actions of ETs on the striatal dopaminergic system.
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| 7698191 |
Blockade of feeding inhibition by neuromedin B using a selective receptor antagonist |
10.1016/0014-2999(94)90291-7. |
Eur J Pharmacol |
Blockade of feeding inhibition by neuromedin B using a selective receptor antagonist
Abstract
- The ability of a selective neuromedin B receptor antagonist, D-Nal-cycloCys-Tyr-D-Trp-Orn-Val-Cys-Nal-NH2 (BIM-23127), to block suppression of food intake produced by the mammalian bombesin-like peptides neuromedin B and neuromedin C was examined. BIM-23127 completely blocked suppression of intake produced by neuromedin B but not by neuromedin C. These results suggest an independent role for neuromedin B receptors in suppression of food intake by bombesin-like peptides and demonstrate the utility of this group of antagonists for in vivo experiments.
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| 7700849 |
Role of endogenous cyclo(His-Pro) in cold-induced hypothermia in the desert rat (Mastomys natalensis) |
10.1016/0196-9781(94)90125-2. |
Peptides |
Role of endogenous cyclo(His-Pro) in cold-induced hypothermia in the desert rat (Mastomys natalensis)
Abstract
- Central administration of exogenous cyclo(His-Pro) (CHP) is known to produce hypothermia in rodents. In the present study, we examined the role of endogenous CHP in cold-induced hypothermia in the desert rat, Mastomys natalensis. The results of these studies show that a rise in hypothalamic CHP content accompanied a decrease in rectal temperature during cold exposure. Immuutralization of endogenous CHP resulted in a significant decline in cold-induced hypothermia. In addition, central administration of cyclo(Ala-Gly), a structural analogue of CHP, also led to a decrease in cold-induced hypothermia. The results of these studies show that changes in endogenous CHP levels may affect body temperature regulation.
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| 7703226 |
Elucidation of the primary and three-dimensional structure of the uterotonic polypeptide kalata B1 |
10.1021/bi00013a002. |
Biochemistry |
Elucidation of the primary and three-dimensional structure of the uterotonic polypeptide kalata B1
Abstract
- The amino acid sequence and structure of a uterotonic polypeptide extracted from the African plant Oldenlandia affinis DC have been determined. The peptide, kalata B1, consists of 29 amino acid residues and is rich in cysteine (6), threonine (5), and glycine (5). Enzyme cleavage studies show that the polypeptide backbone is cyclic. The three-dimensional solution structure has been determined using two-dimensional nuclear magnetic resonance (NMR) spectroscopy and distance-restrained simulated annealing. Kalata B1 is composed mainly of beta-strands connected by tight turns, forming regions of beta-sheet, except in the case of one section which forms a longer, less structured loop. The tertiary fold, together with the disulfides that form a sulfur core, produces a striking and unusual surface in which the majority of the hydrophobic residues form a solvent-exposed patch. The hydrophobic side of kalata B1 is flanked by two diametrically opposed and opposite-charged residues. The structure calculations have been used to predict the previously unknown disulfide bond connectivities using two approaches. In the first, a family of structures was calculated on the basis of NOE constraints without the assumption of a specific disulfide connectivity. The resultant structures were examined to determine whether the calculated position of the sulfur atoms suggested that one set of disulfide connectivities was more likely than the other, theoretically possible, sets. In the second approach, a separate family of structures (50 per set) was calculated for each of the 15 possible disulfide-bonded molecules. The resultant families of structures were compared to see whether one was favored over the others. Both approaches led to the same global fold, and the most likely disulfide connectivity is predicted to be 5-22, 13-27, and 17-29. In the calculated structure the cyclic peptide backbone is folded back onto itself and braced with disulfide pairs across diagonally opposed beta-strands. This structure involves one of the disulfide bonds (5-22) threading through the eight amino acid loop formed by the other two disulfide bonds and the peptide fragments connecting them.
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| 7712125 |
Design of a potent and orally active nonpeptide platelet fibrinogen receptor (GPIIb/IIIa) antagonist |
10.1016/s0968-0896(00)82039-8. |
Bioorg Med Chem |
Design of a potent and orally active nonpeptide platelet fibrinogen receptor (GPIIb/IIIa) antagonist
Abstract
- The direct design of the potent nonpeptide platelet fibrinogen receptor (GPIIb/IIIa) antagonist, 8-4- (aminoiminomethyl)phenylaminocarbonyl-2,3,4,5-tetrahydro-3-oxo- 4- (2-phenylethyl)-1H-1,4-benzodiazepine-2-acetic acid, (3) (SB 207448), based on the structure and conformation of the potent and highly constrained cyclic peptide antagonist SK&F 107260 (2), has been reported Ku et al., J. Am. Chem. Soc. 1993, 115, 8861. While 3 displayed in vivo activity in the conscious dog following intravenous administration, it was not active following intraduodenal administration; activity was measured with an ex vivo platelet aggregation assay. The secondary amide in 3 was N-methylated in the expectation of increased absorption and bioavailability. The resulting tertiary amide, 4 (SB 208651), also showed high binding affinity for human GPIIb/IIIa and potent antiaggregatory activity in human platelet-rich plasma. Most importantly, 4 was active in vivo following intravenous and intraduodenal administration. Comparison of the iv and id inhibition curves suggests an apparent bioavailability of approximately 10%. Thus, 4 represents the first orally active compound in this series of potent, nonpeptide fibrinogen receptor antagonists.
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| 7714530 |
Cyclopsychotride A, a biologically active, 31-residue cyclic peptide isolated from Psychotria longipes |
10.1021/np50114a002. |
J Nat Prod |
Cyclopsychotride A, a biologically active, 31-residue cyclic peptide isolated from Psychotria longipes
Abstract
- A preliminary characterization is provided of a naturally occurring cyclic peptide with interesting and potent biological activity. A 31-residue cyclic peptide, designated cyclopsychotride A 1, was obtained from the organic extract of the tropical plant, Psychotria longipes. Compound 1 inhibited 125I neurotensin (NT) binding to HT-29 cell membranes (IC50 3 microM) and also stimulated increased levels of cytosolic Ca2+ in two unrelated cell lines that do not express NT receptors. The peptide was found to dose-dependently increase intracellular Ca2+ at concentrations ranging from 3 to 30 microM, and this response was not blocked by a known NT antagonist. Cyclopsychotride A 1 possesses three disulfide linkages and is thought to be the largest cyclic peptide isolated from a natural source. Both 1H-nmr and cd spectroscopy showed 1 to be highly structured.
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| 7715451 |
Amoebapores, a family of membranolytic peptides from cytoplasmic granules of Entamoeba histolytica: isolation, primary structure, and pore formation in bacterial cytoplasmic membranes |
10.1111/j.1365-2958.1994.tb01325.x. |
Mol Microbiol |
Amoebapores, a family of membranolytic peptides from cytoplasmic granules of Entamoeba histolytica: isolation, primary structure, and pore formation in bacterial cytoplasmic membranes
Abstract
- Three peptides with pore-forming activity were isolated from the cytoplasmic granules of pathogenic Entamoeba histolytica by acidic extraction, gel filtration and reversed-phase high-performance liquid chromatography. Partial amino acid sequence analysis of the three active peptides revealed that the most abundant of them was amoebapore and the other two were isoforms thereof. Cloning and sequencing of genomic DNA resolved the amino acid sequence of the two newly recognized peptides. The three peptides designated amoebapores A, B and C were found to have the same molecular size but to differ markedly in their primary structure, although all six cysteine residues are conserved. Despite sequence divergence, structural implications predict for the three peptides a similar amphipathic alpha-helical conformation stabilized by disulphide bonds. All three isoforms exhibit pore-forming activity toward lipid vesicles, but they differ in their kinetics. They also are capable of perturbing the integrity of bacterial cytoplasmic membranes and thereby kill Gram-positive bacteria. The amoebapores represent a distinct family of membrane-active peptides that may function intracellularly as antimicrobial agents but may also confer cytolytic activity on the parasite.
|
| 7716522 |
Crystal structure of the mammalian Grb2 adaptor |
10.1126/science.7716522. |
Science |
Crystal structure of the mammalian Grb2 adaptor
Abstract
- The mammalian growth factor receptor-binding protein Grb2 is an adaptor that mediates activation of guanine nucleotide exchange on Ras. Grb2 binds to the receptor through its SH2 domain and to the carboxyl-terminal domain of Son of sevenless through its two SH3 domains. It is thus a key element in the signal transduction pathway. The crystal structure of Grb2 was determined to 3.1 angstrom resolution. The asymmetric unit is composed of an embedded dimer. The interlaced junctions between the SH2 and SH3 domains bring the two adjacent faces of the SH3 domains in van der Waals contact but leave room for the binding of proline-rich peptides.
|
| 7717999 |
Mitochondrial non-specific pores remain closed during cardiac ischaemia, but open upon reperfusion |
10.1042/bj3070093. |
Biochem J |
Mitochondrial non-specific pores remain closed during cardiac ischaemia, but open upon reperfusion
Abstract
- 1. The yield of mitochondria isolated from perfused hearts subjected to 30 min ischaemia followed by 15 min reperfusion was significantly less than that for control hearts, and this was associated with a decrease in the rates of ADP-stimulated respiration. 2. The presence of 0.2 microM cyclosporin A (CsA) in the perfusion medium during ischaemia and reperfusion caused mitochondrial recovery to return to control values, but did not reverse the inhibition of respiration. 3. A technique has been devised to investigate whether the Ca(2+)-induced non-specific pore of the mitochondrial inner membrane opens during ischaemia and/or reperfusion of the isolated rat heart. The protocol involved loading the heart with 2-deoxy3Hglucose (3HDOG), which will only enter mitochondria when the pore opens. Subsequent isolation of mitochondria demonstrated that 3HDOG did not enter mitochondria during global isothermic ischaemia, but did enter during the reperfusion period. 4. The amount of 3HDOG that entered mitochondria increased with the time of ischaemia, and reached a maximal value after 30-40 min of ischaemia. 5. CsA at 0.2 microM did not prevent 3HDOG becoming associated with the mitochondria, but rather increased it; this was despite CsA having a protective effect on heart function similar to that shown previously Griffiths and Halestrap (1993) J. Mol. Cell. Cardiol. 25, 1461-1469. 6. The non-immunosuppressive CsA analogue MeAla6cyclosporin was shown to have a similar Ki to CsA on purified mitochondrial peptidyl-prolyl cis-trans-isomerase and mitochondrial pore opening, and also to have a similar protective effect against reperfusion injury. 7. Using isolated heart mitochondria, it was demonstrated that pore opening could become CsA-insensitive under conditions of adenine nucleotide depletion and high matrix Ca2+ such as may occur during the initial phase of reperfusion. The apparent increase in mitochondrial 3HDOG in the CsA-perfused hearts is explained by the ability of the drug to stabilize pore closure and so decrease the loss of 3HDOG from the mitochondria during their preparation.
|
| 7720653 |
Alternative splicing of a 48-nucleotide exon generates two isoforms of the human calcitonin receptor. |
10.1210/endo.136.5.7720653 |
Endocrinology |
Alternative splicing of a 48-nucleotide exon generates two isoforms of the human calcitonin receptor.
Abstract
- A portion of the human calcitonin receptor (hCTR) gene corresponding to the region of the porcine gene at which alternative splicing generates two CTR isoforms was isolated by polymerase chain reaction amplification of placental DNA. In contrast to the porcine CTR gene, in which two acceptor sites in exon 8 are separated by 48 nucleotides, we found a distinct 48-nucleotide exon in the hCTR gene that is present approximately 6400 basepairs from the up-stream exon, which corresponds to porcine exon 7, and approximately 1100 basepairs from the down-stream exon, which corresponds to porcine exon 8. Splicing of this exon accounts for the two isoforms of hCTR, containing or not containing a 16-amino acid insertion in the first putative intracellular loop. A region similar to the intron 7-exon junction in the porcine CTR gene is present in the human gene, but contains four extra nucleotides that shift the reading frame. Using probes derived from these introns in somatic cell and in situ hybridization analyses, we assigned the CTR gene to human chromosome band 7q21.2-q21.3. Thus, human and porcine species have evolved distinct mechanisms to generate two similar CTR isoforms.
|
| 7730157 |
Inhibition of the binding of oxidized low density lipoprotein to the macrophages by iturin C-related compounds |
10.7164/antibiotics.48.226. |
J Antibiot (Tokyo) |
Inhibition of the binding of oxidized low density lipoprotein to the macrophages by iturin C-related compounds
Abstract
- Binding of modified lipoproteins including oxidized low density lipoprotein (oxidized LDL) to cell surface receptors is an initial step of conversion of monocyte-derived macrophages into lipid-laden foam cells, a key cellular component in the early lesions of atherosclerosis. We have searched for microbial metabolites that inhibit oxidized LDL-induced lipid accumulation in macrophages and isolated three compounds from a strain of Bacillus sp. as inhibitors of oxidized LDL binding. By chemical and spectroscopic analyses, these metabolites were shown to be related to the cyclic lipopeptide iturin C. Two of these compounds were novel metabolites having long chain beta-amino acid moieties of different length. These agents, at concentrations ranging from 5 to 20 microM, inhibited cell surface binding of oxidized 125I-LDL, resulting in reduced intracellular accumulation and degradation of the lipoprotein as well as in reduced cholesteryl ester formation from 14Coleate in macrophages J774.
|
| 7733942 |
Species difference in the binding characteristics of RES-701-1: potent endothelin ETB receptor-selective antagonist |
10.1006/bbrc.1995.1557. |
Biochem Biophys Res Commun |
Species difference in the binding characteristics of RES-701-1: potent endothelin ETB receptor-selective antagonist
Abstract
- Species-dependency of RES-701-1 (cyclic (Gly1-Asp9)(Gly-Asn-Trp-His-Gly-Thr-Ala-Pro-Asp-Trp-Phe-Phe- Asn-Tyr-Tyr-Trp)) has been shown using 125I-ET-1 binding to membranes from various animal tissues. RES-701-1 selectively inhibited the 125I-ET-1 binding to ETB receptor from canine, rabbit, porcine, and guinea pig lung tissues in a dose-dependent manner with IC50 values of 60 nM, 20, 4 nM and 13 nM, respectively. Though RES-701-1 retained selectivity for ETB receptor even at higher concentrations, RES-701-1 inhibited the 125I-ET-1 binding to ETB receptor from rat lung, heart, and kidney only weakly; IC50 values were calculated to be 1.2 microM, 0.9 microM and 0.6 microM, respectively. These results suggest that RES-701-1 is a potent and specific antagonist for ETB receptor in various species of animal, and would be a powerful tool for understanding the physiological roles of ETB receptor, but care must be taken in use of RES-701-1 in experiments with rat.
|
| 7733946 |
A new type of human calcitonin receptor isoform generated by alternative splicing. |
10.1006/bbrc.1995.1562 |
Biochem. Biophys. Res. Commun. |
A new type of human calcitonin receptor isoform generated by alternative splicing.
Abstract
- There are three isoforms of calcitonin receptors (CTRs). The first type (type 1) has 479 amino acids in rat and 482 amino acids in porcine. The second type (type 2) has a 39 amino acid insertion in the second extracellular domain. The third type (type 3) has a 16 amino acid insertion in the first intracellular domain. The CTR which has been isolated from a human ovarian carcinoma cell line belongs to type 3. Using RT-PCR with primers whose sequences correspond to the human CTR cDNA, we analyzed the expression of the CTR transcripts in seven human tumor cell lines and surgical specimens. The CTR m-RNA were found in all samples. Transcripts which were 48bp shorter than that of the type 3 human CTR were detected, but not transcripts of type 2 and type 3. Since the structure of this CTR is same as that of the type 1 rat and porcine CTRs, we termed it the human type 1 CTR. PCR studies using human genomic DNA as a template revealed that the 48bp sequence constitutes an exon. These
Results indicate that the type 1 and the type 3 human CTRs are generated by alternative splicing and a majority of human CTR transcripts is type 1.
|
| 7735216 |
Molecular parameters for the anti-human immunodeficiency virus activity of T22 (Tyr5,12, Lys7-polyphemusin II) |
10.1248/bpb.17.1669. |
Biol Pharm Bull |
Molecular parameters for the anti-human immunodeficiency virus activity of T22 (Tyr5,12, Lys7-polyphemusin II)
Abstract
- T22 (Tyr5,12, Lys7-polyphemusin II) was found to exhibit strong anti-human immunodeficiency virus (HIV) activity and exert its effects on a virus-cell fusion process. In the present study, the all-D enantiomer of T22 and its related compounds were synthesized to examine the molecular parameters required for the interaction of T22 with membrane components of cells or viruses in order to exert this anti-HIV activity. The anti-HIV activity of these analogs was investigated in comparison with their membrane permeability with aspect to large unilamellar vesicles (LUVs). The all-D enantiomer of T22 exhibited a 20-fold lower anti-HIV activity compared with T22, whereas they both showed the same membrane permeability. No positive correlation between anti-HIV activity and membrane permeability was observed. These results suggest that the anti-HIV activity of T22 is mediated through the interaction with chiral component(s) of the cell or virus.
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