| 11841212 |
Crystal structure of Vat(D): an acetyltransferase that inactivates streptogramin group A antibiotics. |
10.1021/bi011991b |
Biochemistry |
Crystal structure of Vat(D): an acetyltransferase that inactivates streptogramin group A antibiotics.
Abstract
- The streptogramin class of antibiotics act to inhibit bacterial protein synthesis, and their semisynthetic derivatives, such as dalfopristin-quinupristin (Synercid), are used to treat serious or life-threatening infections due to multiply antibiotic resistant bacteria. Acquired resistance of the nosocomial pathogen Enterococcus faecium to the group A component of natural and semisynthetic streptogramin mixtures is a prerequisite for the streptogramin resistance phenotype and is mediated by a streptogramin acetyltransferase. The crystal structure of Vat(D), a streptogramin acetyltransferase from a human urinary isolate of E. faecium, has been determined as an apoenzyme and in complex with either acetyl-CoA or virginiamycin M1 and CoA. These structures illustrate the location and arrangement of residues at the active site, and point to His 82 as a residue that may function as a general base. The structural similarity of Vat(D) to the xenobiotic acetyltransferase from Pseudomonas aeruginosa indicates similarities in the catalytic mechanism for these enzymes as well as several shared and distinctive antibiotic binding interactions between these enzymes and their respective substrates. These
Results reveal the molecular basis for a reaction by which Gram-positive cocci acquire resistance to a last resort antibiotic.
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| 11851477 |
Multifunctional Peptide Synthetases |
10.1021/cr9600262. |
Chem Rev |
Multifunctional Peptide Synthetases
Abstract
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| 11856024 |
Structure and chemistry of apicidins, a class of novel cyclic tetrapeptides without a terminal alpha-keto epoxide as inhibitors of histone deacetylase with potent antiprotozoal activities |
10.1021/jo016088w. |
J Org Chem |
Structure and chemistry of apicidins, a class of novel cyclic tetrapeptides without a terminal alpha-keto epoxide as inhibitors of histone deacetylase with potent antiprotozoal activities
Abstract
- Apicidins are a class of cyclic tetrapeptides that do not contain the classical electrophilic alpha-keto epoxide yet are potent (nM) inhibitors of histone deacetylase and antiprotozoal agents. These compounds showed broad-spectrum activities against the apicomplexan family of protozoa including Plasmodium sp (malarial parasite), Toxoplasma gondii, Cryptosporidium sp., and Eimeria sp. These cyclic peptides contain a beta-turn amino acid (R)-Pip or (R)-Pro, (S)-N-methoxy Trp, (S)-Ile, or (S)-Val, and either (S)-2-amino-8-oxodecanoic acid or a modified (S)-2-amino-8-oxodecanoic acid. The isolation and structure elucidation of new apicidins from two Fusarium species, temperature-dependent NMR studies of apicidin, NMR and molecular modeling based conformation of the 12-membered macrocyclic ring, and selected chemical modifications of apicidin have been detailed in this paper. The cyclic nature of the peptide, the C-8 keto group, and the tryptophan are all critical for the biological activity.
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| 11864635 |
The human tachykinin NK1 (short form) and tachykinin NK4 receptor: a reappraisal |
10.1016/s0014-2999(02)01278-5. |
Eur J Pharmacol |
The human tachykinin NK1 (short form) and tachykinin NK4 receptor: a reappraisal
Abstract
- Excessive secretion of placental neurokinin B into the circulation during the third trimester of pregnancy is seen in women with preeclampsia. To determine a role for neurokinin B, we have used a number of different animal models to ascertain the expression of the three tachykinin receptors (NK1--both short and long forms, NK2 and NK3) and the putative human tachykinin NK4 receptor in the placenta. Human and rat placenta express all three classical tachykinin receptors. However, we failed to reveal the expression of the short tachykinin NK1 receptor or the tachykinin NK4 receptor in any of 24 human tissues examined including the placenta. We conclude that the proposed short form of the tachykinin NK1 receptor is a truncated genomic clone and that the human tachykinin NK4 receptor is in fact, the guinea pig tachykinin NK3 receptor.
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| 11866271 |
Mutational screening of patients with nonalcoholic chronic pancreatitis: identification of further trypsinogen variants |
10.1111/j.1572-0241.2002.05467.x. |
Am J Gastroenterol |
Mutational screening of patients with nonalcoholic chronic pancreatitis: identification of further trypsinogen variants
Abstract
- Objectives:
Mutations of the cationic trypsinogen (CT) and the serine protease inhibitor, Kazal type 1 (SPINK 1) are associated with chronic pancreatitis. After mutational screening of a cohort of patients with nonalcoholic chronic pancreatitis, we report three novel variants of the trypsinogen molecule and the clinical characteristics of the carriers.
Methods:
The coding region of the exon 2 and 3 of the CT gene of 523 patients with chronic nonalcoholic pancreatitis (108 patients with suspected hereditary pancreatitis (HP) and 415 patients with "idio pathic" pancreatitis [IP]) and 82 controls was analyzed after polymerase chain reaction amplification. Clinical characteristics were obtained by questioning the patients and their relatives and physicians. HP was suspected when two members of a family had chronic pancreatitis. A restriction digestion was used to analyze the N34S mutation SPINK1.
Results:
The mutation R122H of the cationic trypsinogen was found in 21 index patients, N291 in six index patients, and A16V and D22G in one index patient, all from HP families. The N34S mutation of SPINK1 was found in two index patients with a family history of HP. In three patients, the novel point mutations L104P, R116C, and C139F of the cationic trypsinogen were found. A clear autosomally dominant inheritance of chronic pancreatitis was not present in these families. In 75 index patients from HP families (69.4%), no mutation could be found. The SPINK 1-mutation N34S was detected in only one patient carrying a CT mutation, and was found in 68 (16.4%) of patients with IP.
Conclusions:
The R122H and N291 mutations of CT are the most common disease-associated mutations in HP; the N34S mutation of SPINK I is the most frequent genetic risk factor associated with IP. The CT gene carries several variations that could be associated with chronic pancreatitis. To avoid overestimating the pathogenetic impact of novel trypsinogen variants, a detailed clinical characterization of all patients with early onset chronic pancreatitis is mandatory.
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| 11867090 |
The destruxins: synthesis, biosynthesis, biotransformation, and biological activity |
10.1016/s0031-9422(02)00016-x. |
Phytochemistry |
The destruxins: synthesis, biosynthesis, biotransformation, and biological activity
Abstract
- Destruxins, secondary metabolites first reported in 1961, are cyclic hexadepsipeptides composed of an alpha-hydroxy acid and five amino acid residues. The name "destruxin" is derived from "destructor" from the species Oospora destructor, the entomopathogenic fungus from which these metabolites were first isolated. Individual destruxins differ on the hydroxy acid, N-methylation, and R group of the amino acid residues; where established, the configurations of the amino acid residues are S, and those of the hydroxy acids are R. Destruxins exhibit a wide variety of biological activities, but are best known for their insecticidal and phytotoxic activities. The great interest in destruxins derives from their potential role as virulence factors in fungi, whether such microorganisms are useful insect biocontrol agents or detrimental, causing great plant disease epidemics. Reports on isolation, chemical structure determination, total synthesis, transformation by diverse organisms, and biological activity of destruxins and related metabolites are reviewed for the first time.
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| 11872202 |
Alternatively spliced variants of the follicle-stimulating hormone receptor gene in the testis of infertile men. |
10.1016/s0015-0282(01)03221-6 |
Fertil. Steril. |
Alternatively spliced variants of the follicle-stimulating hormone receptor gene in the testis of infertile men.
Abstract
- Objective: To investigate whether or not alternatively spliced variants of the FSH receptor gene occur in human testis and whether the presence of the splicing variants is associated with spermatogenic defects and serum FSH concentration in infertile men. Design: A prospective case control study. Setting: An IVF clinic and infertility laboratory at a university hospital. Patient(s): Forty-three infertile patients undergoing testicular biopsy. Intervention(s): Total RNA was extracted from the testicular tissues and used for reverse transcriptase-polymerase chain reaction (RT-PCR). Main outcome measure(s): Expression pattern was analyzed by nested RT-PCR using primers designed to amplify a fragment of FSH receptor gene. PCR products of splicing variants were cloned and sequenced. Result(s): The PCR products showed three kinds of additional bands corresponding to alternatively spliced isoforms of the FSH receptor gene. Exon 9 deleted variant was detected in all patients and inclusion variant of small extra exon was detected in 64% (9/14) of the patients with normal spermatogenesis and 34% (10/29) of the patients with spermatogenic defects. The presence of inclusion variant was not significantly associated with spermatogenic defects but was associated with a low level of serum FSH. On the other hand, exon 6 deleted variant was detected in only one patient having a high level of FSH concentration (30 IU/L) and Sertoli cell only syndrome. Conclusion(s): We identified three different types of alternatively spliced variants of the human FSH receptor. However, it is not clear whether or not there is an association between three variants and spermatogenic defects.
|
| 11875025 |
The human ribosomal protein genes: sequencing and comparative analysis of 73 genes |
10.1101/gr.214202. |
Genome Res |
The human ribosomal protein genes: sequencing and comparative analysis of 73 genes
Abstract
- The ribosome, as a catalyst for protein synthesis, is universal and essential for all organisms. Here we describe the structure of the genes encoding human ribosomal proteins (RPs) and compare this class of genes among several eukaryotes. Using genomic and full-length cDNA sequences, we characterized 73 RP genes and found that (1) transcription starts at a C residue within a characteristic oligopyrimidine tract; (2) the promoter region is GC rich, but often has a TATA box or similar sequence element; (3) the genes are small (4.4 kb), but have as many as 5.6 exons on average; (4) the initiator ATG is in the first or second exon and is within plus minus 5 bp of the first intron boundaries in about half of cases; and (5) 5'- and 3'-UTRs are significantly smaller (42 bp and 56 bp, respectively) than the genome average. Comparison of RP genes from humans, Drosophila melanogaster, Caenorhabditis elegans, and Saccharomyces cerevisiae revealed the coding sequences to be highly conserved (63% homology on average), although gene size and the number of exons vary. The positions of the introns are also conserved among these species as follows: 44% of human introns are present at the same position in either D. melanogaster or C. elegans, suggesting RP genes are highly suitable for studying the evolution of introns.
|
| 11882916 |
Somatostatin (SRIF) modulates distinct signaling pathways in rat pituitary tumor cells; negative coupling of SRIF receptor subtypes 1 and 2 to arachidonic acid release |
10.1007/s00210-001-0509-7. |
Naunyn Schmiedebergs Arch Pharmacol |
Somatostatin (SRIF) modulates distinct signaling pathways in rat pituitary tumor cells; negative coupling of SRIF receptor subtypes 1 and 2 to arachidonic acid release
Abstract
- The somatotropin release-inhibiting factor somatostatin-14 (SRIF) is known to activate distinct receptor subtypes (sst1-5). In rat pituitary tumor cells (GC cells), sst2 but not sst1 receptors mediate the SRIF-induced inhibition of intracellular concentration of Ca2+ ([Ca2+]i) and are negatively coupled to cAMP-dependent pathways. In the present study, transduction mechanisms coupling distinct SRIF receptors to their specific functional role were investigated with the use of both SRIF agonists with well-known affinity at individual SRIF receptors and the sst2 receptor antagonist L-Tyr(8) isomer of Cyanamid 154806 (CYN-154806). Our results demonstrate that sst1 and sst2 receptors are coupled to distinct signaling pathways in GC cells. In particular, sst2 receptors are negatively coupled to the cAMP-dependent pathway and this pathway is partially responsible for the sst2 receptor-mediated inhibition of [Ca2+]i. In addition, sst1 and sst2 receptors are both coupled to a decrease of arachidonic acid (AA) release with an efficacy similar to that of SRIF, suggesting that SRIF reduces AA release through either a partial activation of both receptors or the activation of one at a time. This finding is important given the well-accepted role for phospholipase A2 (PLA2) as a positive signaling component in transduction pathways of SRIF receptors. sst1 and sst2 receptor negative coupling to PLA2/AA pathways does not seem to be implicated in the SRIF-induced inhibition of [Ca2+]i. The possible role for the SRIF-mediated inhibition of AA release in GC cell function remains to be elucidated.
|
| 11884618 |
RACK1, an insulin-like growth factor I (IGF-I) receptor-interacting protein, modulates IGF-I-dependent integrin signaling and promotes cell spreading and contact with extracellular matrix |
10.1128/MCB.22.7.2345-2365.2002. |
Mol Cell Biol |
RACK1, an insulin-like growth factor I (IGF-I) receptor-interacting protein, modulates IGF-I-dependent integrin signaling and promotes cell spreading and contact with extracellular matrix
Abstract
- The insulin-like growth factor I (IGF-I) receptor (IGF-IR) is known to regulate a variety of cellular processes including cell proliferation, cell survival, cell differentiation, and cell transformation. IRS-1 and Shc, substrates of the IGF-IR, are known to mediate IGF-IR signaling pathways such as those of mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K), which are believed to play important roles in some of the IGF-IR-dependent biological functions. We used the cytoplasmic domain of IGF-IR in a yeast two-hybrid interaction trap to identify IGF-IR-interacting molecules that may potentially mediate IGF-IR-regulated functions. We identified RACK1, a WD repeat family member and a Gbeta homologue, and demonstrated that RACK1 interacts with the IGF-IR but not with the closely related insulin receptor (IR). In several types of mammalian cells, RACK1 interacted with IGF-IR, protein kinase C, and beta1 integrin in response to IGF-I and phorbol 12-myristate 13-acetate stimulation. Whereas most of RACK1 resides in the cytoskeletal compartment of the cytoplasm, transformation of fibroblasts and epithelial cells by v-Src, oncogenic IR or oncogenic IGF-IR, but not by Ros or Ras, resulted in a significantly increased association of RACK1 with the membrane. We examined the role of RACK1 in IGF-IR-mediated functions by stably overexpressing RACK1 in NIH 3T3 cells that expressed an elevated level of IGF-IR. RACK1 overexpression resulted in reduced IGF-I-induced cell growth in both anchorage-dependent and anchorage-independent conditions. Overexpression of RACK1 also led to enhanced cell spreading, increased stress fibers, and increased focal adhesions, which were accompanied by increased tyrosine phosphorylation of focal adhesion kinase and paxillin. While IGF-I-induced activation of IRS-1, Shc, PI3K, and MAPK pathways was unaffected, IGF-I-inducible beta1 integrin-associated kinase activity and association of Crk with p130(CAS) were significantly inhibited by RACK1 overexpression. In RACK1-overexpressing cells, delayed cell cycle progression in G(1) or G(1)/S was correlated with retinoblastoma protein hypophophorylation, increased levels of p21(Cip1/WAF1) and p27(Kip1), and reduced IGF-I-inducible Cdk2 activity. Reduction of RACK1 protein expression by antisense oligonucleotides prevented cell spreading and suppressed IGF-I-dependent monolayer growth. Our data suggest that RACK1 is a novel IGF-IR signaling molecule that functions as a positive mediator of cell spreading and contact with extracellular matrix, possibly through a novel IGF-IR signaling pathway involving integrin and focal adhesion signaling molecules.
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| 11889179 |
A Novel mutation in the FSH receptor inhibiting signal transduction and causing primary ovarian failure |
10.1210/jcem.87.3.8319. |
J Clin Endocrinol Metab |
A Novel mutation in the FSH receptor inhibiting signal transduction and causing primary ovarian failure
Abstract
- Inactivating mutations of the FSH receptor (FSHR) are known to cause ovarian failure with amenorrhea and infertility in women. The first mutation identified in the FSHR gene was a missense mutation (566C-->T, predicting Ala189Val transition) found in several Finnish patients with primary amenorrhea due to ovarian failure. Only five additional, partially or totally inactivating, mutations of the FSHR have been reported. Here, we report a novel FSHR mutation, 1255G-->A, in a Finnish female with primary amenorrhea. The patient was a compound heterozygote for two mutations in the FSHR gene: 566C-->T, the Finnish founder mutation, and 1255G-->A, a previously unidentified mutation. The new mutation is located in exon 10 in the second transmembrane stretch of the FSHR, and it predicts an Ala419Thr change in the protein structure. In functional testing, the mutation was shown to have minimal effect on ligand binding capacity and affinity, but it almost totally abolished the cAMP second messenger response. Neither of the two FSHR mutations (566C-->T or1255G-->A) was identified in 40 other Finnish patients with premature ovarian failure. Based on this and previous studies, FSHR mutations remain a rare cause of ovarian failure.
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| 11891250 |
Snakin-2, an antimicrobial peptide from potato whose gene is locally induced by wounding and responds to pathogen infection |
10.1104/pp.010685. |
Plant Physiol |
Snakin-2, an antimicrobial peptide from potato whose gene is locally induced by wounding and responds to pathogen infection
Abstract
- The peptide snakin-2 (StSN2) has been isolated from potato (Solanum tuberosum cv Jaerla) tubers and found to be active (EC(50) = 1-20 microM) against fungal and bacterial plant pathogens. It causes a rapid aggregation of both Gram-positive and Gram-negative bacteria. The corresponding StSN2 cDNA encodes a signal sequence followed by a 15-residue acidic sequence that precedes the mature StSN2 peptide, which is basic (isoelectric point = 9.16) and 66 amino acid residues long (molecular weight of 7,025). The StSN2 gene is developmentally expressed in tubers, stems, flowers, shoot apex, and leaves, but not in roots, or stolons, and is locally up-regulated by wounding and by abscisic acid treatment. Expression of this gene is also up-regulated after infection of potato tubers with the compatible fungus Botritys cinerea and down-regulated by the virulent bacteria Ralstonia solanacearum and Erwinia chrysanthemi. These observations are congruent with the hypothesis that the StSN2 is a component of both constitutive and inducible defense barriers.
|
| 11895390 |
Kulokekahilide-1, a cytotoxic depsipeptide from the cephalaspidean mollusk Philinopsis speciosa |
10.1021/jo010176z. |
J Org Chem |
Kulokekahilide-1, a cytotoxic depsipeptide from the cephalaspidean mollusk Philinopsis speciosa
Abstract
- The cytotoxic depsipeptide kulokekahilide-1, which contains two unusual amino acids, 4-phenylvaline and 3-amino-2-methylhexanoic acid, was isolated from the cephalaspidean mollusk Philinopsis speciosa. Structure elucidation of kulokekahilide-1 was carried out by spectroscopic analysis and chemical degradation. The absolute stereochemistry was determined by Marfey analysis for amino acids and chiral HPLC analysis for hydroxy acids. All four stereoisomers of 4-phenylvaline and 3-amino-2-methylhexanoic acid, which were necessary for Marfey analysis, were synthesized by use of the Heck reaction and Evans's method, respectively. Kulokekahilide-1 showed cytotoxicity against P388 murine leukemia cells with an IC(50) value of 2.1 microg/mL.
|
| 11897046 |
A novel 196Leu to Pro substitution in the beta3 subunit of the alphaIIbbeta3 integrin in a patient with a variant form of Glanzmann thrombasthenia |
10.1080/09537100220122466. |
Platelets |
A novel 196Leu to Pro substitution in the beta3 subunit of the alphaIIbbeta3 integrin in a patient with a variant form of Glanzmann thrombasthenia
Abstract
- Glanzmann thrombasthenia (GT) is an inherited disorder where an absence of platelet aggregation is associated with quantitative or qualitative abnormalities of the alphaIIbbeta3 integrin. In rare patients, amino acid substitutions have provided information on the functional significance of specific domains within alphaIIb or beta3. We now report an elderly male GT patient (R.M.) from the south west of France whose platelets possess a small residual expression of alphaIIbbeta3. Furthermore, the integrin failed to undergo the necessary conformational changes following platelet activation to permit the binding of fibrinogen or activation-dependent monoclonal antibodies despite the presence of an RGD-binding site. Screening of the alphaIIb and beta3 genes by PCR-SSCP revealed a heterozygous mutation at position 685 in exon 5 of the beta3 gene leading to a 196Leu to Pro substitution. 196Leu is a highly conserved amino acid of beta3. The other beta3 allele appeared to be silent. This mutation, inherited from his mother and present in other family members with intermediate levels of alphaIIbbeta3, was close to the MIDAS-like domain of beta3, a fact that appears to explain its effect on alphaIIbbeta3 activation and fibrinogen binding.
|
| 11908961 |
Cyclotheonamide E4 and E5, new potent tryptase inhibitors from an Ircinia species of sponge |
10.1021/np010304e. |
J Nat Prod |
Cyclotheonamide E4 and E5, new potent tryptase inhibitors from an Ircinia species of sponge
Abstract
- Tryptase is a protease released from mast cells and is believed to contribute to the inflammatory process in allergic diseases including asthma. In the course of screening to find tryptase inhibitors, we isolated two new tryptase inhibitors, cyclotheonamide E4 (3) and E5 (4), from a marine sponge of the genus Ircinia. The structures of these molecules were determined by interpretation of 1H and 13C NMR spectra, and they were shown to be closely related to the previously reported cyclotheonamides E (1), E2, and E3 (2). These molecules contain two unusual amino acids, vinylogous tyrosine and alpha-ketohomoarginine, which are involved in strong activities against serine proteases. Cyclotheonamide E4 showed potent inhibitory activity against human tryptase (IC50 5.1 nM). Therefore, cyclotheonamide E4 may be useful as a therapeutic agent in the treatment of allergic diseases including asthma.
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