| 9233773 |
Cloning and characterization of APS, an adaptor molecule containing PH and SH2 domains that is tyrosine phosphorylated upon B-cell receptor stimulation |
10.1038/sj.onc.1201163. |
Oncogene |
Cloning and characterization of APS, an adaptor molecule containing PH and SH2 domains that is tyrosine phosphorylated upon B-cell receptor stimulation
Abstract
- Stimulation of B lymphocytes through their antigen receptor (BCR) results in rapid increases in tyrosine phosphorylation of a number of proteins, which leads to a cascade of biochemical changes that initiates B cell proliferation and differentiation or growth inhibition. A novel cDNA, designed APS, encoding an adaptor protein with a Pleckstrin homology (PH) domain, Src homology 2 (SH2) domain, and a tyrosine phosphorylation site was cloned from a B cell cDNA library using a yeast two hybrid system. APS is structurally similar to SH2-B, an SH2 protein that potentially binds to the immunoreceptor tyrosine-based activation motif (ITAM) as well as Lnk which is postulated to be a signal transducer that links T-cell receptor to phospholipase Cgamma, Grb2 and phosphatidylinositol 3-kinase. APS expressed only in human Burkitt's lymphoma cells among cell lines we examined and tyrosine phosphorylated in response to BCR stimulation. APS bound to Shc irrespective of stimulation and bound to Grb2 after stimulation, suggesting that it plays a role in linkage from BCR to Shc/Grb2 pathway. These results indicate that APS, SH2-B and Lnk form a new adaptor family that links immune receptors to signaling pathways involved in tyrosine-phosphorylation.
|
| 9234331 |
(2-18Ffluoropropionyl-(D)phe1)-octreotide, a potential radiopharmaceutical for quantitative somatostatin receptor imaging with PET: synthesis, radiolabeling, in vitro validation and biodistribution in mice |
10.1016/0969-8051(94)90161-9. |
Nucl Med Biol |
(2-18Ffluoropropionyl-(D)phe1)-octreotide, a potential radiopharmaceutical for quantitative somatostatin receptor imaging with PET: synthesis, radiolabeling, in vitro validation and biodistribution in mice
Abstract
- Octreotide is labeled with fluorine-18 as a potential radiopharmaceutical for quantitative in vivo mapping of somatostatin receptors. 18F-fluoroacylation is achieved with n.c.a. 2-18Ffluoropropionic acid 4-nitrophenylester which is reacted with epsilon-Boc-Lys5-octreotide. After deprotection the desired N alpha-18Ffluoropropionylated octreotide (18FSDZ 223-228) is obtained. Final HPLC purification gives rise to radiochemical yields of 65 +/- 5% based on the fluoroacylation agent. Binding experiments using rat cortex membranes indicate an affinity for somatostatin receptors of pKi = 8.6 +/- 0.2. The biological activity of this SRIF analog is demonstrated by the inhibition of growth hormone release from cultured pituitary cells. The pIC50 in this test system is 8.75, indicating full biological activity. Biodistribution studies with NMRI mice show predominantly renal excretion, rapid blood clearance and only negligible bone activity, i.e. formation of free fluoride.
|
| 9237346 |
Isolation and identification of 12 microcystins from four strains and two bloom samples of Microcystis spp.: structure of a new hepatotoxin |
10.1016/0041-0101(94)90030-2. |
Toxicon |
Isolation and identification of 12 microcystins from four strains and two bloom samples of Microcystis spp.: structure of a new hepatotoxin
Abstract
- Sixteen microcystins, cyclic heptapeptide hepatotoxins, were isolated and purified by high performance liquid chromatography (HPLC) and thin layer chromatography (TLC) from four hepatotoxic strains and two Microcystis spp. bloom samples originating from five different lakes in Finland. The structures of a new Dha7MCYST-FR and 11 known microcystins MCYST-LR, D-Asp3MCYST-LR, Dha7MCYST-LR, D-Asp3, Dha7 MCYST-LR, MCYST-RR, D-Asp3MCYST-RR, Dha7MCYST-RR, D-Asp3,Dha7MCYST-RR, L-Ser7MCYST-RR, MCYST-YR and Dha7 MCYST-YR were assigned based on amino acid analysis, fast atom bombardment mass spectrometry (FABMS) and tandem FABMS. Four other new compounds allowed only determination of their molecular formulas and amino acid components because of inadequate amounts obtained. Dha7MCYST-RR was found most frequently in these samples as the main toxin.
|
| 9240381 |
Sensitivity of periodontal pathogens to the bactericidal activity of synthetic protegrins, antibiotic peptides derived from porcine leukocytes |
10.1177/00220345970760080701. |
J Dent Res |
Sensitivity of periodontal pathogens to the bactericidal activity of synthetic protegrins, antibiotic peptides derived from porcine leukocytes
Abstract
- Protegrins, small peptides (1900 to 2160 daltons) isolated from porcine leukocytes, are bactericidal against a broad range of medical pathogens in vitro under conditions which reflect the extracellular milieu. The purpose of this study was to determine whether Gram-negative, facultative periodontal pathogens were sensitive to the protegrins. Synthetic L- and D-enantiomers of protegrin 1 (PG-1 and D-PG-1, respectively), and L-enantiomers of protegrins 2, 3, and 5 (PG-2, PG-3, and PG-5) were tested against Actinobacillus actinomycetemcomitans (three strains) and Capnocytophaga spp. (three strains). Strains of both A. actinomycetemcomitans and Capnocytophaga spp. were sensitive to PG-1, and exhibited ED99 (dose at which 99% killing was observed after 1 hr at 37 degrees C) of 0.5 to 3 microg/mL and 4 to 19 microg/mL, respectively. The D-form and the L-form were equally effective. Serum (above 5% v/v) inhibited the bactericidal effects of 10 microg/mL PG-1, but the inhibitory effect was overcome by concentrations of PG-1 at 100 microg/mL. Different patterns of sensitivity were observed when the effects of PG-1, D-PG-1, PG-2, PG-3, and PG-5 were compared against A. actinomycetemcomitans and the Capnocytophaga. We conclude that protegrins may be useful antimicrobial agents in therapy against periodontal infections.
|
| 9245817 |
Enterocin B, a new bacteriocin from Enterococcus faecium T136 which can act synergistically with enterocin A |
10.1099/00221287-143-7-2287. |
Microbiology (Reading) |
Enterocin B, a new bacteriocin from Enterococcus faecium T136 which can act synergistically with enterocin A
Abstract
- The strain Enterococcus faecium T136 produces two bacteriocins, enterocin A, a member of the pediocin family of bacteriocins, and a new bacteriocin termed enterocin B. The N-terminal amino acid sequences of enterocins A and B were determined, and the gene encoding enterocin B was sequenced. The primary translation product was a 71 aa peptide containing a leader peptide of the double-glycine type which is cleaved off to give mature enterocin B of 53 aa. Enterocin B does not belong to the pediocin family of bacteriocins and shows strong homology to carnobacteriocin A. However, sequence similarities in their leader peptides and C-termini suggest that enterocin B and carnobacteriocin A are related to bacteriocins of the pediocin family. Enterocins A and B had only slightly different inhibitory spectra, and both were active against a wide range of Gram-positive bacteria, including listeriae, staphylococci and most lactic acid bacteria tested. Both had bactericidal activities, but survival at a frequency of 10(-4)-10(-2) was observed when sensitive cultures were exposed to either bacteriocin. The number of survivors was drastically reduced when a mixture of the two bacteriocins was added to the cells.
|
| 9249867 |
Molecular analysis of the insulin receptor gene for prenatal diagnosis of leprechaunism in two families |
None |
Prenat Diagn |
Molecular analysis of the insulin receptor gene for prenatal diagnosis of leprechaunism in two families
Abstract
- Leprechaunism is a rare autosomal recessive disorder characterized by marked intrauterine and postnatal growth retardation, severe insulin resistance, and altered glucose homeostasis. This syndrome is related to mutations in the insulin receptor (IR) gene that impair the transmission of the insulin signal by several mechanisms. There is no effective therapy and patients usually die within the first months of life. Here we report the prenatal diagnosis of leprechaunism in two unrelated families in which affected children were compound heterozygotes with two different deficient IR alleles. In family Par-1, the disease IR alleles carried a missense mutation located in exon 18 (Arg1092-->Trp) and exon 20 (Glu1179-->Lys). In family Als, a 3-basepair deletion causing the loss of Asn281 in exon 3 and a major deletion of exons 10-13 were present in the maternal and paternal mutant IR alleles, respectively. Prenatal diagnosis was made in each family by a specific approach combining denaturing gradient gel electrophoresis (DGGE) and Southern blotting. This methodology allowed us to correctly predict the genotype of the two fetuses at the IR locus.
|
| 9249979 |
Kawaguchipeptin B, an antibacterial cyclic undecapeptide from the cyanobacterium Microcystis aeruginosa |
10.1021/np970146k. |
J Nat Prod |
Kawaguchipeptin B, an antibacterial cyclic undecapeptide from the cyanobacterium Microcystis aeruginosa
Abstract
- Kawaguchipeptin B, an antibacterial cyclic undecapeptide, was isolated from the cultured cyanobacterium Microcystis aeruginosa (NIES-88). Its structure was elucidated as 1 on the basis of 2D NMR data and chemical degradation. Kawaguchipeptin B (1) inhibited the growth of the Gram-positive bacterium Staphylococcus aureus at a concentration of 1 microgram/mL (MIC).
|
| 9272723 |
MEN 11,420, a peptide tachykinin NK2 receptor antagonist, reduces motor responses induced by the intravesical administration of capsaicin in vivo |
10.1007/pl00005039. |
Naunyn Schmiedebergs Arch Pharmacol |
MEN 11,420, a peptide tachykinin NK2 receptor antagonist, reduces motor responses induced by the intravesical administration of capsaicin in vivo
Abstract
- This study investigates the role of tachykinin NK1 and NK2 receptors in motor responses induced by the intravesical instillation of capsaicin in urethane-anaesthetized rats. SR 140,333 (1 micromol/kg, i.v.), a nonpeptide NK1 receptor antagonist, abolished urinary bladder contractions induced by the selective NK1 receptor agonist Sar9SP-sulfone (0.1-100 nmol/kg, i.v.) without affecting those induced by the NK2 receptor agonist betaAla8NKA(4-10). MEN 11,420 (100 nmol/kg, i.v.), a cyclic peptide NK2 receptor antagonist, abolished bladder contractions induced by betaAla8NKA(4-10) (0.3-300 nmol/kg, i.v.) without modifying those induced by Sar9SP-sulfone. Intravesical instillation of capsaicin (6 nmol/0.6 ml/rat) produced a motor response consisting in a primary contraction followed by a series of high amplitude phasic contractions. The intravesical instillation of saline (0.6 ml/rat) produced a primary contraction of lower amplitude with respect to that induced by capsaicin and the total area under the curve was also lower in saline-instilled rats, however the number and the amplitude of phasic contractions was similar to that induced by capsaicin. MEN 11,420 (100 nmol/kg, i.v.) did not modify motor responses induced by the intravesical administration of saline. In contrast, in capsaicin-instilled rats, MEN 11,420 (100 nmol/kg, i.v.) reduced the primary contraction, the area under the curve and also the number of phasic contractions. SR 140,333 (1 micromol/kg, i.v.) reduced the primary contraction but not other parameters. The combination of SR 140,333 (1 micromol/kg, i.v.) and MEN 11,420 (100 nmol/kg, i.v.) produced an additive inhibitory effect on the primary contraction but not a further inhibition on other parameters with respect to that observed with MEN 11,420 alone. In hexamethonium (110 micromol/kg, i.v.)-pretreated animals the intravesical instillation of capsaicin produced a tonic contraction having greater amplitude and area than that induced by saline. MEN 11,420, but not SR 140,333, significantly reduced the bladder response to capsaicin in hexamethonium-pretreated rats. Again, the combined administration of MEN 11,420 and SR 140,333 did not produce further inhibitory effect in comparison to MEN 11,420 alone. It is concluded that the motor responses induced by the intravesical instillation of capsaicin are mediated by the activation of peripheral tachykinin NK2 receptors.
|
| 9276132 |
Role of tachykinin NK1 and NK2 receptors on colonic motility in anesthetized rats: effect of agonists |
None |
Can J Physiol Pharmacol |
Role of tachykinin NK1 and NK2 receptors on colonic motility in anesthetized rats: effect of agonists
Abstract
- Tachykinins fulfill general criteria to be considered as neurotransmitters-neuroeffectors in the mammalian enteric nervous system; however, little information is available about their role in the regulation of intestinal motility in vivo. The present study investigates the effect of selective tachykinin receptor agonists on colonic motility in urethane-anesthetized rats. Colonic motility was recorded by means of a balloon-catheter device (filled with 0.5 mL of water) inserted for 7 cm through the rectum. In atropine- and guanethidine-pretreated rats, the NK1 receptor agonist Sar9substance P sulfone (0.3-300 nmol/kg i.v.) dose dependently induced phasic contractions followed by an enhancement in the amplitude and frequency of spontaneous contractions. In three of six cases, a transient inhibition (3-5 min) of spontaneous motility was also evident after the phasic contraction. All these effects were reduced by the NK1 receptor antagonist SR 140333 (1 mumol/kg i.v.). In atropine- and guanethidine-pretreated rats and in the presence of SR 140333 (1 mumol/kg i.v.), the NK2 receptor agonist beta-Ala8neurokinin A-(4-10) (0.3-300 nmol/kg i.v.) induced a dose-dependent tonic contraction, but the amplitude and frequency of spontaneous contractions were not changed. NK2 receptor antagonists such as MEN 11420 (0.01-1 mumol/kg i.v.), MEN 10627 (1 mumol/kg i.v.), or SR 48968 (1 mumol/kg i.v.) reduced the effect of beta-Ala8neurokinin A-(4-10). The present results indicate that NK2 receptor stimulation evokes a pure excitatory effect on colonic motility whereas NK1 receptor stimulation induces both excitatory and inhibitory effects.
|
| 9278503 |
The complete genome sequence of Escherichia coli K-12 |
10.1126/science.277.5331.1453 |
Science (New York, N.Y.) |
The complete genome sequence of Escherichia coli K-12
Abstract
- The 4,639,221-base pair sequence of Escherichia coli K-12 is presented. Of 4288 protein-coding genes annotated, 38 percent have no attributed function. Comparison with five other sequenced microbes reveals ubiquitous as well as narrowly distributed gene families; many families of similar genes within E. coli are also evident. The largest family of paralogous proteins contains 80 ABC transporters. The genome as a whole is strikingly organized with respect to the local direction of replication; guanines, oligonucleotides possibly related to replication and recombination, and most genes are so oriented. The genome also contains insertion sequence (IS) elements, phage remnants, and many other patches of unusual composition indicating genome plasticity through horizontal transfer.
|
| 9287217 |
A broad-spectrum chemokine antagonist encoded by Kaposi's sarcoma-associated herpesvirus |
10.1126/science.277.5332.1656. |
Science |
A broad-spectrum chemokine antagonist encoded by Kaposi's sarcoma-associated herpesvirus
Abstract
- Kaposi's sarcoma-associated herpesvirus encodes a chemokine called vMIP-II. This protein displayed a broader spectrum of receptor activities than any mammalian chemokine as it bound with high affinity to a number of both CC and CXC chemokine receptors. Binding of vMIP-II, however, was not associated with the normal, rapid mobilization of calcium from intracellular stores; instead, it blocked calcium mobilization induced by endogenous chemokines. In freshly isolated human monocytes the virally encoded vMIP-II acted as a potent and efficient antagonist of chemotaxis induced by chemokines. Because vMIP-II could inhibit cell entry of human immunodeficiency virus (HIV) mediated through CCR3 and CCR5 as well as CXCR4, this protein may serve as a lead for development of broad-spectrum anti-HIV agents.
|
| 9290212 |
Sequence analysis of 203 kilobases from Saccharomyces cerevisiae chromosome VII. |
10.1002/(sici)1097-0061(19970915)13:11<1077::aid-yea152>3.0.co |
Yeast |
Sequence analysis of 203 kilobases from Saccharomyces cerevisiae chromosome VII.
Abstract
- The nucleotide sequences of five major regions from chromosome VII of Saccharomyces cerevisiae have been determined and analysed. These regions represent 203 kilobases corresponding to approximately one-fifth of the complete yeast chromosome VII. Two fragments originate from the left arm of this chromosome. The first one of about 15.8 kb starts approximately 75 kb from the left telomere and is bordered by the SK18 chromosomal marker. The second fragment covers the 72.6 kb region between the chromosomal markers CYH2 and ALG2. On the right chromosomal arm three regions, a 70.6 kb region between the MSB2 and the KSS1 chromosomal markers and two smaller regions dominated by the KRE11 marker and another one in the vicinity of the SER2 marker were sequenced. We found a total of 114 open reading frames (ORFs), 13 of which were completely overlapping with larger ORFs running in the opposite direction. A total of 44 yeast genes, the physiological functions of which are known, could be precisely mapped on this chromosome. Of the remaining 57 ORFs, 26 shared sequence homologies with known genes, among which were 13 other S. cerevisiae genes and five genes from other organisms. No homology with any sequence in the databases could be found for 31 ORFs. Furthermore, five Ty elements were found, one of which may not be functional due to a frame shift in its Ty1B amino acid sequence. The five chromosomal regions harboured five potential ARS elements and one sigma element together with eight tRNA genes and two snRNAs, one of which is encoded by an intron of a protein-coding gene.
|
| 9295302 |
Membrane topology of the multidrug resistance protein (MRP). A study of glycosylation-site mutants reveals an extracytosolic NH2 terminus. |
10.1074/jbc.272.38.23623 |
J. Biol. Chem. |
Membrane topology of the multidrug resistance protein (MRP). A study of glycosylation-site mutants reveals an extracytosolic NH2 terminus.
Abstract
- Multidrug resistance protein, MRP, is a 190-kDa integral membrane phosphoglycoprotein that belongs to the ATP-binding cassette superfamily of transport proteins and is capable of conferring resistance to multiple chemotherapeutic agents. Previous studies have indicated that MRP consists of two membrane spanning domains (MSD) each followed by a nucleotide binding domain, plus an additional extremely hydrophobic NH2-terminal MSD. Computer-assisted hydropathy analyses and multiple sequence alignments suggest several topological models for MRP. To aid in determining the topology most likely to be correct, we have identified which of the 14 N-glycosylation sequons in this protein are utilized. Limited proteolysis of MRP-enriched membranes and deglycosylation of intact MRP and its tryptic fragments with PNGase F was carried out followed by immunoblotting with antibodies known to react with specific regions of MRP. The
Results obtained indicated that the sequon at Asn354 in the middle MSD is not utilized and suggested approximate sites of N-glycosylation. Subsequent site-directed mutagenesis studies established that Asn19 and Asn23 in the NH2-terminal MSD and Asn1006 in the COOH-terminal MSD are the only sites in MRP that are modified with N-linked oligosaccharides. N-Glycosylation of Asn19 and Asn23 provides the first direct experimental evidence that MRP has an extracytosolic NH2 terminus. This finding, together with those of previous studies, strongly suggests that the NH2-terminal MSD of MRP contains an odd number of transmembrane helices. These
Results may have important implications for the further understanding of the interaction of drugs with MRP.
|
| 9298951 |
Crystal structure at 1.1 A resolution of alpha-conotoxin PnIB: comparison with alpha-conotoxins PnIA and GI |
10.1021/bi9713052. |
Biochemistry |
Crystal structure at 1.1 A resolution of alpha-conotoxin PnIB: comparison with alpha-conotoxins PnIA and GI
Abstract
- Conotoxins are small, cysteine-rich peptides isolated from the venom of Conus spp. of predatory marine snails, which selectively target specific receptors and ion channels critical to the functioning of the neuromuscular system. alpha-Conotoxins PnIA and PnIB are both 16-residue peptides (differing in sequence at only two positions) isolated from the molluscivorous snail Conus pennaceus. In contrast to the muscle-selective alpha-conotoxin GI from Conus geographus, PnIA and PnIB block the neuronal nicotinic acetylcholine receptor (nAChR). Here, we describe the crystal structure of PnIB, solved at a resolution of 1.1 A and phased using the Shake-and-Bake direct methods program. PnIB crystals are orthorhombic and belong to the space group P212121 with the following unit cell dimensions: a = 14.6 A, b = 26.1 A, and c = 29.2 A. The final refined structure of alpha-conotoxin PnIB includes all 16 residues plus 23 solvent molecules and has an overall R-factor of 14.7% (R-free of 15.9%). The crystal structures of the alpha-conotoxins PnIB and PnIA are solved from different crystal forms, with different solvent contents. Comparison of the structures reveals them to be very similar, showing that the unique backbone and disulfide architecture is not strongly influenced by crystal lattice constraints or solvent interactions. This finding supports the notion that this structural scaffold is a rigid support for the presentation of important functional groups. The structures of PnIB and PnIA differ in their shape and surface charge distribution from that of GI.
|
| 9299395 |
Four mutant alleles of the insulin receptor gene associated with genetic syndromes of extreme insulin resistance |
10.1006/bbrc.1997.7181. |
Biochem Biophys Res Commun |
Four mutant alleles of the insulin receptor gene associated with genetic syndromes of extreme insulin resistance
Abstract
- We identified four novel mutant alleles of the insulin receptor gene in three patients with genetic syndromes associated with insulin resistance. Two mutant alleles of the insulin receptor gene were identified in a patient with the Rabson-Mendenhall syndrome who was a compound heterozygote for a mutation at the 3'-splice acceptor site of intron 4 (AG-->GG), the first mutation causing an aberrant splicing at this locus, and a deletion of eight base pairs in exon 12. The second patient with leprechaunism was also a compound heterozygote for a deletion of one base pair in exon 19 and a mutation, Thr910-->Met, which causes impaired receptor processing. Interestingly, the third patient with type A syndrome was a simple heterozygote for the identical one base pair deletion. The fact that the same one base pair deletion links to type A in a simple heterozygote and to leprechaunism in a compound heterozygote appears consistent with the hypothesis that the severity of mutations will determine the phenotype.
|
