| 15664516 |
Specificity and affinity of natural product cyclopentapeptide inhibitors against A. fumigatus, human, and bacterial chitinases |
10.1016/j.chembiol.2004.10.013 |
Chemistry & biology |
Specificity and affinity of natural product cyclopentapeptide inhibitors against A. fumigatus, human, and bacterial chitinases
Abstract
- Family 18 chitinases play key roles in organisms ranging from bacteria to man. There is a need for specific, potent inhibitors to probe the function of these chitinases in different organisms. Such molecules could also provide leads for the development of chemotherapeuticals with fungicidal, insecticidal, or anti-inflammatory potential. Recently, two natural product peptides, argifin and argadin, have been characterized, which structurally mimic chitinase-chitooligosaccharide interactions and inhibit a bacterial chitinase in the nM-mM range. Here, we show that these inhibitors also act on human and Aspergillus fumigatus chitinases. The structures of these enzymes in complex with argifin and argadin, together with mutagenesis, fluorescence, and enzymology, reveal that subtle changes in the binding site dramatically affect affinity and selectivity. The data show that it may be possible to develop specific chitinase inhibitors based on the argifin/argadin scaffolds.
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| 15667208 |
Disulfide bond mutagenesis and the structure and function of the head-to-tail macrocyclic trypsin inhibitor SFTI-1 |
10.1021/bi048297r. |
Biochemistry |
Disulfide bond mutagenesis and the structure and function of the head-to-tail macrocyclic trypsin inhibitor SFTI-1
Abstract
- SFTI-1 is a novel 14 amino acid peptide comprised of a circular backbone constrained by three proline residues, a hydrogen-bond network, and a single disulfide bond. It is the smallest and most potent known Bowman-Birk trypsin inhibitor and the only one with a cyclic peptidic backbone. The solution structure of [ABA(3,11)]SFTI-1, a disulfide-deficient analogue of SFTI-1, has been determined by (1)H NMR spectroscopy. The lowest energy structures of native SFTI-1 and [ABA(3,11)]SFTI-1 are similar and superimpose with a root-mean-square deviation over the backbone and heavy atoms of 0.26 +/- 0.09 and 1.10 +/- 0.22 A, respectively. The disulfide bridge in SFTI-1 was found to be a minor determinant for the overall structure, but its removal resulted in a slightly weakened hydrogen-bonding network. To further investigate the role of the disulfide bridge, NMR chemical shifts for the backbone H(alpha) protons of two disulfide-deficient linear analogues of SFTI-1, [ABA(3,11)]SFTI-1[6,5] and [ABA(3,11)]SFTI-1[1,14] were measured. These correspond to analogues of the cleavage product of SFTI-1 and a putative biosynthetic precursor, respectively. In contrast with the cyclic peptide, it was found that the disulfide bridge is essential for maintaining the structure of these open-chain analogues. Overall, the hydrogen-bond network appears to be a crucial determinant of the structure of SFTI-1 analogues.
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| 15670714 |
Expression of agsA, one of five 1,3-alpha-D-glucan synthase-encoding genes in Aspergillus niger, is induced in response to cell wall stress. |
10.1016/j.fgb.2004.11.006 |
Fungal Genet. Biol. |
Expression of agsA, one of five 1,3-alpha-D-glucan synthase-encoding genes in Aspergillus niger, is induced in response to cell wall stress.
Abstract
- 1,3-alpha-D-Glucan is an important component of the cell wall of filamentous fungi. We have identified a family of five 1,3-alpha-D-glucan synthase-encoding genes in Aspergillus niger. The agsA gene was sequenced and the predicted protein sequence indicated that the overall domain structure of 1,3-alpha-D-glucan synthases is conserved in fungi. Using RT-PCR and Northern blot analysis, we found that expression of the agsA gene and to a lesser extent also of agsE were induced in the presence of the cell wall stress-inducing compounds such as Calcofluor White (CFW), SDS, and caspofungin. Loss of agsA function did not result in an apparent phenotype under normal growth conditions but rendered the cells more sensitive to CFW. The induction of 1,3-alpha-D-glucan synthase-encoding genes in response to cell wall stress was not limited to A. niger, but was also observed in Penicillium chrysogenum. We propose that this response to cell wall stress commonly occurs in filamentous fungi.
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| 15673735 |
Mutation of tlyA confers capreomycin resistance in Mycobacterium tuberculosis. |
10.1128/aac.49.2.571-577.2005 |
Antimicrob. Agents Chemother. |
Mutation of tlyA confers capreomycin resistance in Mycobacterium tuberculosis.
Abstract
- Capreomycin, an important drug for the treatment of multidrug-resistant tuberculosis, is a macrocyclic peptide antibiotic produced by Saccharothrix mutabolis subspecies capreolus. The basis of resistance to this drug was investigated by isolating and characterizing capreomycin-resistant strains of Mycobacterium smegmatis and Mycobacterium tuberculosis. Colonies resistant to capreomycin were recovered from a library of transposon-mutagenized M. smegmatis. The transposon insertion site of one mutant was mapped to an open reading frame in the unfinished M. smegmatis genome corresponding to the tlyA gene (Rv1694) in the M. tuberculosis H37Rv genome. In M. smegmatis spontaneous capreomycin-resistant mutants, the tlyA gene was disrupted by one of three different naturally occurring insertion elements. Genomic DNAs from pools of transposon mutants of M. tuberculosis H37Rv were screened by PCR by using primers to the tlyA gene and the transposon to detect mutants with an insertion in the tlyA gene. One capreomycin-resistant mutant was recovered that contained the transposon inserted at base 644 of the tlyA gene. Complementation with the wild-type tlyA gene restored susceptibility to capreomycin in the M. smegmatis and M. tuberculosis tlyA transposon mutants. Mutations were found in the tlyA genes of 28 spontaneous capreomycin-resistant mutants generated from three different M. tuberculosis strains and in the tlyA genes of capreomycin-resistant clinical isolates. In in vitro transcription-translation assays, ribosomes from tlyA mutant but not tlyA(+) strains resist capreomycin inhibition of transcription-translation. Therefore, TlyA appears to affect the ribosome, and mutation of tlyA confers capreomycin resistance.
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| 15679310 |
Two new chymotrypsin inhibitors isolated from the Cyanobacterium Microcystis aeruginosa NIES-88 |
10.1021/np0401361. |
J Nat Prod |
Two new chymotrypsin inhibitors isolated from the Cyanobacterium Microcystis aeruginosa NIES-88
Abstract
- Micropeptins 88-N (1) and 88-Y (2), new 3-amino-6-hydroxy-2-piperidone (Ahp)-containing cyclic depsipeptides, were isolated from Microcystis aeruginosa NIES-88. The structures were elucidated by analyses of HRFABMS, 1D and 2D NMR spectra, and chemical degradation. Micropeptins 88-N and 88-Y inhibited chymotrypsin. The inhibitory activities were closely related to the amino acid residue that was attached to the amino group of Ahp.
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| 15679318 |
Isolation and structure of phakellistatin 14 from the Western Pacific marine sponge Phakellia sp |
10.1021/np040092w. |
J Nat Prod |
Isolation and structure of phakellistatin 14 from the Western Pacific marine sponge Phakellia sp
Abstract
- A new cycloheptapeptide, phakellistatin 14, was isolated in 8.8 x 10(-7)% yield from Phakellia sp., a marine sponge from Chuuk, Federated States of Micronesia. The structure (1), cyclo-Phe-beta-OMe-Asp-Ala-Met(SO)-Ala-Ile-Pro, was elucidated by 1D and 2D NMR spectral analyses augmented by HRFABMS. The chirality of each amino acid unit was determined to be S using chiral HPLC methods. Phakellistatin 14 showed cancer cell growth inhibitory activity (ED(50) 5 microg/mL) against the murine lymphocytic leukemia P388 cell line.
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| 15705855 |
A selective inhibitor of eIF2alpha dephosphorylation protects cells from ER stress. |
10.1126/science.1101902 |
Science |
A selective inhibitor of eIF2alpha dephosphorylation protects cells from ER stress.
Abstract
- Most protein phosphatases have little intrinsic substrate specificity, making selective pharmacological inhibition of specific dephosphorylation reactions a challenging problem. In a screen for small molecules that protect cells from endoplasmic reticulum (ER) stress, we identified salubrinal, a selective inhibitor of cellular complexes that dephosphorylate eukaryotic translation initiation factor 2 subunit alpha (eIF2alpha). Salubrinal also blocks eIF2alpha dephosphorylation mediated by a herpes simplex virus protein and inhibits viral replication. These
Results suggest that selective chemical inhibitors of eIF2alpha dephosphorylation may be useful in diseases involving ER stress or viral infection. More broadly, salubrinal demonstrates the feasibility of selective pharmacological targeting of cellular dephosphorylation events.
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| 15730251 |
Brevicompanine C, cyclo-(D-Ile-L-Trp), and cyclo-(D-Leu-L-Trp), plant growth regulators from Penicillium brevi-compactum |
10.1021/np040178p. |
J Nat Prod |
Brevicompanine C, cyclo-(D-Ile-L-Trp), and cyclo-(D-Leu-L-Trp), plant growth regulators from Penicillium brevi-compactum
Abstract
- New plant growth regulators, named brevicompanine C (1), cyclo-(D-Ile-L-Trp) (2), and cyclo-(D-Leu-L-Trp) (3), have been isolated from Penicillium brevi-compactum Dierckx, and their structures have been established by spectroscopic methods including 2D NMR and chiral TLC analysis. Plant growth activities of 1, 2, and 3 have been examined using lettuce seedling bioassay methods. All compounds accelerated the root growth of the seedlings in proportion to their concentration from 1 to 100 mg/L.
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| 15738637 |
Receptor-type protein tyrosine phosphatase epsilon (PTPepsilonM) is a negative regulator of insulin signaling in primary hepatocytes and liver |
10.2108/zsj.22.169. |
Zoolog Sci |
Receptor-type protein tyrosine phosphatase epsilon (PTPepsilonM) is a negative regulator of insulin signaling in primary hepatocytes and liver
Abstract
- Impaired insulin receptor (IR) signaling leads to insulin resistance and type 2 diabetes mellitus. Several inhibitors of the IR tyrosine kinase activity have recently been described and associated with human insulin resistance. Among these negative regulators, protein tyrosine phosphatases (PTPs) are likely to play a pivotal role in IR signaling. Transgenic studies revealed that PTP1B and TCPTP are primary candidates but IR of these animals can be finally dephosphorylated, suggesting that other PTPs are also involved in the dephosphorylation of IR. In this study, we showed that receptor-type PTPepsilon (PTP epsilonM) dephosphorylated IR in rat primary hepatocytes and tyrosines 972, 1158, 1162 and 1163 were primary targets of PTP epsilonM. Wild type as well as substrate-trapping DA forms of PTPepsilonM suppressed phosphorylation of IR downstream enzymes such as Akt, extracellular regulated kinase (ERK) and glycogen synthase kinase 3 (GSK3). It was also demonstrated that PTPepsilonM suppressed insulin-induced glycogen synthesis and inhibited insulin-induced suppression of phosphoenol pyruvate carboxykinase (PEPCK) expression in primary hepatocytes. Furthermore, adenovirally introduced PTPepsilonM also exhibited inhibitory activity against suppression of PEPCK expression in mouse liver. These results suggest that PTPepsilonM is a negative regulator of IR signaling and involved in insulin-induced glucose metabolism mainly through direct dephosphorylation and inactivation of IR in hepatocytes and liver.
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| 15743176 |
Solid-phase total synthesis of kahalalide A and related analogues |
10.1021/jm049841x. |
J Med Chem |
Solid-phase total synthesis of kahalalide A and related analogues
Abstract
- The marine natural product kahalalide A, a cyclic depsipeptide, was prepared by total synthesis on solid-phase. A backbone cyclization strategy was followed, using the Kenner sulfonamide safety-catch linker. By NMR comparison of synthetic and naturally isolated material, the stereochemistry of the methylbutyrate side chain was established as (S). Several analogues were synthesized and tested for antimycobacterial activity. The results indicate that the alcohol functional group in the serine and threonine residues is important, while the methylbutyrate side chain can be replaced by an achiral hexanoate with an increase in activity.
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| 15744111 |
Longicalycinin A, a new cytotoxic cyclic peptide from Dianthus superbus var. longicalycinus (MAXIM.) WILL |
10.1248/cpb.53.336. |
Chem Pharm Bull (Tokyo) |
Longicalycinin A, a new cytotoxic cyclic peptide from Dianthus superbus var. longicalycinus (MAXIM.) WILL
Abstract
- A new cyclic peptide, longicalycinin A (1), and six known compounds, vaccaroside A, dianoside A, dianoside G, 3-(4-hydroxy-3-methoxy-phenyl)propionic acid methyl ester, p-hydroxybenzoic acid, and p-hydroxybenzaldehyde were isolated from the MeOH extract of Dianthus superbus var. longicalycinus. The amino acid sequences of 1 was elucidated as cyclo(Gly(1)-Phe(2)-Tyr(3)-Pro(4)-Phe(5)-) on the basis of ESI tandem mass fragmentation analysis, chemical evidence, and extensive 2D NMR methods. Furthermore, compound 1 showed cytotoxicity to Hep G2 cancer cell line.
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| 15748237 |
Mutations in GPIIIa molecule as a cause for Glanzmann thrombasthenia in Indian patients |
10.1111/j.1538-7836.2005.01159.x. |
J Thromb Haemost |
Mutations in GPIIIa molecule as a cause for Glanzmann thrombasthenia in Indian patients
Abstract
- Background:
Glanzmann thrombasthenia (GT) results from a quantitative or qualitative defect of GPIIb-IIIa complex, the fibrinogen receptor on platelets, which plays a very important role in platelet aggregation. In this report we describe the molecular studies on 22 patients with Glanzmann Thrombasthenia at our institute.
Objectives:
The main objective was to identify the mutations present in our GT population in order to establish a strategy for genetic counseling and antenatal diagnosis.
Methods:
Twenty-two patients with GT were included in the present study. Complete blood count (CBC), platelet aggregation, flow cytometry, Western blot, single strand conformation polymorphism (SSCP) and denaturing gradient gel electrophoresis (DGGE) were performed in all the patients. The patients showing an abnormal migration pattern in SSCP or DGGE were sequenced further on an automated sequencer.
Results:
Of the 22 patients studied, mutations were detected in 12 individuals. Of these, 11 were novel mutations and one mutation Y115C was reported earlier. Flow cytometric analysis showed the absence of receptors in type I GT, highly reduced levels in type II GT and normal levels in type III GT. The DGGE analysis and SSCP analysis of the patients showed different migration patterns. Sequencing was performed in all patients showing an abnormal migration pattern. Of the 22 cases studied mutations could be detected in 12 cases of GT. We could detect six patients with point mutations, four patients with insertions and five patients with deletion mutations. Exon 4 has been found to be the most common site for mutations in our patients.
Conclusion:
This study has shown a wide array of mutations present in our GT patients which would be extremely useful in genetic counseling and prenatal diagnosis, essential in preventing these disorders in succeeding generations.
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| 15772651 |
The DNA sequence of the human X chromosome. |
10.1038/nature03440 |
Nature |
The DNA sequence of the human X chromosome.
Abstract
- The human X chromosome has a unique biology that was shaped by its evolution as the sex chromosome shared by males and females. We have determined 99.3% of the euchromatic sequence of the X chromosome. Our analysis illustrates the autosomal origin of the mammalian sex chromosomes, the stepwise process that led to the progressive loss of recombination between X and Y, and the extent of subsequent degradation of the Y chromosome. LINE1 repeat elements cover one-third of the X chromosome, with a distribution that is consistent with their proposed role as way stations in the process of X-chromosome inactivation. We found 1,098 genes in the sequence, of which 99 encode proteins expressed in testis and in various tumour types. A disproportionately high number of mendelian diseases are documented for the X chromosome. Of this number, 168 have been explained by mutations in 113 X-linked genes, which in many cases were characterized with the aid of the DNA sequence.
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| 15776435 |
Gene conversion between functional trypsinogen genes PRSS1 and PRSS2 associated with chronic pancreatitis in a six-year-old girl |
10.1002/humu.20148. |
Hum Mutat |
Gene conversion between functional trypsinogen genes PRSS1 and PRSS2 associated with chronic pancreatitis in a six-year-old girl
Abstract
- Gene conversion--the substitution of genetic material from another gene--is recognized as the underlying cause of a growing number of genetic diseases. While in most cases conversion takes place between a normal gene and its pseudogene, here we report an occurrence of disease-associated gene conversion between two functional genes. Chronic pancreatitis in childhood is frequently associated with mutations of the cationic trypsinogen gene (serine protease 1; PRSS1). We have analyzed PRSS1 in 1106 patients with chronic pancreatitis, and identified a novel conversion event affecting exon 2 and the subsequent intron. The recombination replaced at least 289 nucleotides with the paralogous sequence from the anionic trypsinogen gene (serine protease 2; PRSS2), and resulted in the PRSS1 mutations c.86A > T and c.161A > G, causing the amino acid substitutions N29I and N54S, respectively. Analysis of the recombinant N29I-N54S double mutant cationic trypsinogen revealed increased autocatalytic activation, which was solely due to the N29I mutation. In conclusion, we have demonstrated that gene conversion between two functional paralogous trypsinogen genes can occur and cause genetically determined chronic pancreatitis.
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| 15801827 |
Structures of three classes of anticancer agents bound to the human topoisomerase I-DNA covalent complex |
10.1021/jm049146p. |
J Med Chem |
Structures of three classes of anticancer agents bound to the human topoisomerase I-DNA covalent complex
Abstract
- Human topoisomerase I (top1) is the molecular target of a diverse set of anticancer compounds, including the camptothecins, indolocarbazoles, and indenoisoquinolines. These compounds bind to a transient top1-DNA covalent complex and inhibit the resealing of a single-strand nick that the enzyme creates to relieve superhelical tension in duplex DNA. (Hertzberg, R. P.; et al. Biochem. 1989, 28, 4629-4638. Hsiang, Y. H.; et al. J. Biol. Chem 1985, 260, 14873-14878. Champoux, J. J. Annu. Rev. Biochem. 2001, 70, 369-413. Stewart, L.; et al. Science 1998, 729, 1534-1541.) We report the X-ray crystal structures of the human top1-DNA complex bound with camptothecin and representative members of the indenoisoquinoline and indolocarbazole classes of top1 poisons. The planar nature of all three structurally diverse classes allows them to intercalate between DNA base pairs at the site of single-strand cleavage. All three classes of compounds have a free electron pair near Arg364, a residue that if mutated confers resistance to all three classes of drugs. The common intercalative binding mode is augmented by unexpected chemotype-specific contacts with amino acid residues Asn352 and Glu356, which adopt alternative side-chain conformations to accommodate the bound compounds. These new X-ray structures explain how very different molecules can stabilize top1-DNA covalent complexes and will aid the rational design of completely novel structural classes of anticancer drugs.
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