摘要:

AbstractThe primary structure of the B chain of theN‐acetyl‐D‐galactosamine‐recognizing mistletoe lectin‐3 (ML‐3B) has been deduced from proteolytic digest peptides of the purified glycoprotein, their HPLC‐separation and Edman degradation and confirmation of the peptide sequences by MALDI‐MS. ML‐3B consists of 262 amino acid residues including 10 cysteine moieties. The structure and linkage of the carbohydrate side chains, connected to two N‐glycosylation sites at positions Asn95and Asn135of the lectin, were determined by a combination of glycosidase treatment and MALDI‐MS of corresponding glycopeptide fragments. The sequence alignment reveals a high homology with other B chains of type‐II RIPs, although there are remarkable differences in theD‐galactose‐specific mistletoe lectin‐1B chain. The recently published primary structure of the mistletoe lectin‐3A chain1 and the now available primary sequence of the 3B chain allowed the construction of a preliminary homology model of ML‐3. The model demonstrates, unequivocally, that ML‐3 is a member of the type‐II RIP family with rigid conservation of the enzymatic active site of the A chain and an identical overall protein fold. Specific amino acid residue exchanges and the different glycosylation pattern in comparison with ML‐1 are discussed and related to the properties of the two glycoproteins. The knowledge of the complete primary structure of mistletoe lectin‐3 is a major contribution towards more insight into the mechanism of the biological activity of commercial mistletoe preparations. Copyright © 2004 Europea

ISSN:1075-2617    

DOI:10.1002/psc.627

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractRoutes to oligomers (dimers, tetramers, hexamers) of five oxetane‐based dipeptide isosteres have been established. Methyl 2,4‐anhydro‐5‐azido‐5‐deoxy‐L‐rhamnonate ‘monomer’ led, by coupling the corresponding carboxylic acid and amine, to a ‘dimer’. Reverse‐aldol ring‐opening occurred on attempted saponification of the dimer, so all further oligomerization was performed using TBDMS C‐3 hydroxyl protection. The silyl protectedL‐rhamnonate monomer led in turn to the dimer (via the monomer acid and amine), the tetramer (via the dimer acid and amine) and finally the hexamer (via the tetramer acid and dimer amine). In each case the acids were obtained through saponification of the respective methyl esters and the amines were obtained by hydrogenation of the azides; coupling was TBTU‐mediated. Essentially the same strategy was employed on equivalentD‐lyxonate, 6‐deoxy‐L‐altronate, 6‐deoxy‐D‐gulonate andD‐fuconate dipeptide isosteres to give the respective dimers, tetramers and hexamers. Copyright © 2004

ISSN:1075-2617    

DOI:10.1002/psc.622

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractThe peptide hormones guanylin and uroguanylin are ligands of the intestinal guanylyl cyclase‐C (GC‐C) that is involved in the regulation of epithelial water and electrolyte transport. The small peptides contain 15 and 16 amino acids, respectively, and two disulfide bonds with a 1–3/2–4 connectivity. This structural feature causes the unique existence of two topological isoforms for each peptide in an approximate 3:2 ratio, with only one of the isoforms exhibiting GC‐C‐activating potential. The two uroguanylin isomers can be separated by HPLC and are of sufficient stability to be studied separately at ambient temperatures while the two guanylin isomers are rapidly interconverting even at low temperatures. Both isomers show clearly distinguishable1H chemical shifts. To investigate the influence of certain amino acid side chains on this isomerism and interconversion kinetics, derivatives of guanylin and uroguanylin (L‐alanine scan and chimeric peptides) were designed and synthesized by Fmoc solid‐phase chemistry and compared by HPLC and 2D1H NMR spectroscopy. Amino acid residues with the most significant effects on the interconversion kinetics were predominantly identified in the COOH‐terminal part of both peptides, whereas amino acids in the central part of the peptides only moderately affected the interconversion. Thus, the conformational conversion among the isomers of both peptides is under the control of a COOH‐terminal sterical hindrance, providing a detailed model for this dynamic isomerism. Our results demonstrate that kinetic control of the interconversion process can be achieved by the introduction of side chains with a defined sterical profile at suitable sequence positions. This is of potential impact for the future development of GC‐C peptide agonists and antagonists. Copyright © 2004 European Peptide Society an

ISSN:1075-2617    

DOI:10.1002/psc.625

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractZervamicins (Zrv) IIA and IIB are membrane modifying peptide antibiotics of fungal origin, characterized by a sequence of 15 amino acid residues. The primary structure of Zrv‐IIA contains five α‐aminoisobutyric acid residues at positions 4, 7, 9, 12 and 14 of the linear peptide. The sequence of Zrv‐IIB is similar, but contains aD‐isovaline at position 4. When the free amino acid Aib was added to the peptone‐glucose culture medium, the fungusEmericellopsis salmosynnemataproduced Zrv‐IIA as the major secondary metabolite, whereas addition ofDL‐Iva to the culture led to a high production of Zrv‐IIB. This observation is rationalized by a lack of selectivity of the non‐ribosomal peptide synthetase with respect to the thiolester activated amino acid substrates during step 12 of peptide synthesis. Analysis of the configuration of the Iva residue of Zrv‐IIB showed a high enantiomeric purity of theD‐enantiomer, indicating a high stereoselectivity of the peptide synthetase for this substrate.When the culture was supplemented with [15N]DL‐Iva, the nitrogen isotope was not only found at theD‐Iva residue, but surprisingly also at the Aib residues as well as at the proteinogenic residues of Zrv. The partial catabolism of exogenous [15N]DL‐Iva is explained by the assumption of a decarboxylation‐dependent transamination reaction, catalysed by 2,2‐dimethylglycine decarboxylase. The same enzyme might also be involved in the reversed carboxylation reactions of acetone and 2‐butanone, during the anabolic biosynthesis of Aib and Iva, respectively. Zrv might possibly act as a thermodynamic sink to shift these equilibrium reactions towards the reversed side. Copyright © 2004 European Pepti

ISSN:1075-2617    

DOI:10.1002/psc.621

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractDerivatization of insulin with phenylboronic acids is described, thereby equipping insulin with novel glucose sensing ability. It is furthermore demonstrated that such insulins are useful in glucose‐responsive polymer‐based release systems. The preferred phenylboronic acids are sulfonamide derivatives, which, contrary to naïve boronic acids, ensure glucose binding at physiological pH, and simultaneously operate as handles for insulin derivatization at LysB29. The glucose affinities of the novel insulins were evaluated by glucose titration in a competitive assay with alizarin. The affinities were in the range 15–31 mM(Kd), which match physiological glucose fluctuations. The dose‐responsive glucose‐mediated release of the novel insulins was demonstrated using glucamine‐derived polyethylene glycol polyacrylamide (PEGA) as a model, and it was shown that Zn(II) hexamer formulation of the boronated insulins resulted in steeper glucose sensitivity relative to monomeric insulin formulation. Notably, two of the boronated insulins displayed enhanced insulin receptor affinity relative to native insulin (113%–122%) which is unusual for insulin LysB29 derivatives. Copyright © 2004 European Peptide Society and John

ISSN:1075-2617    

DOI:10.1002/psc.624

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractFour cyclic enkephalin analogues and four cyclic dermorphin analogues have been synthesized. Cyclization of linear peptides containing basic amino acid residues of various side chain length in position 2 and 5 (enkephalin analogues) or 2 and 4 (dermorphin analogues) was achieved by treatment with bis‐(4‐nitrophenyl) carbonate to form a urea unit. The peptides were tested in the guinea‐pig ileum (GPI) and mouse vas deferens (MVD) assays. Diverse activity was observed, depending on the size of the ring and the location of the urea unit. The conformation of two dermorphin analogues has been studied: one of high activity (IC50= 4.15 nMin the GPI assay) and a second of low activity (IC50= 6700 nMin the GPI assay). The conformational space of these peptides was examined using the EDMC method. Using data from the NMR spectra, each peptide was described as an ensemble of conformers. Biological activity was discussed in light of the structural data. Copyright © 2004 European Peptide Society and John Wiley&Son

ISSN:1075-2617    

DOI:10.1002/psc.613

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractMetal‐catalysed oxidation (MCO) may play a causative role in the pathogenesis of Alzheimer's disease (AD). Amyloid β peptide (Aβ), the major biomarker of AD, in the presence of copper ions reduces Cu2+to Cu+and catalyses the formation of H2O2that subsequently induces radicals through Fenton chemistry. Aβ is also subject to attack by free radicals, where the presence of Cu2+in conjunction with H2O2catalyses oxygenation, primarily at the methionine sulfur atom. This work investigates MCO of Aβ, to gain further insight into the role of oxidative stress in AD. By combining a fluorescence assay with gel electrophoresis to monitor MCO reactions of Aβ (1–28) in the presence and absence of methionine it was determined that methionine can both protect some residues against MCO and promote the oxidation of Tyr(10) specifically. Electrospray ionization mass spectrometric analysis of methionine MCO products indicated the formation of methionine sulfoxide, methionine sulfone and related hydroxylated products. Similar products could be formed from the oxidation of Met(35) of Aβ and may relate to changes in properties of the peptide following MCO. Copyright © 2004 European Peptide Society and John Wiley

ISSN:1075-2617    

DOI:10.1002/psc.626

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractTo examine the effect on biological activity of replacingD‐Cys in the opioid peptide H‐Tyr‐c[D‐Cys‐Gly‐Phe(pNO2)‐D‐Cys]‐NH2in position 2 or/and 5 with α‐hydroxymethylcysteine (α‐Hmc), three analogues were synthesized. These compounds exhibit agonist activity at both µ and δ receptors. However, the most active analogue, with (S)‐α‐Hmc residue in position 5, was 3360‐ and 2190‐fold less active than the parent peptide in the GPI and MVD assays, respectively. Copyright © 2004 European Pepti

ISSN:1075-2617    

DOI:10.1002/psc.620

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY