ISSN:1075-2617    

DOI:10.1002/psc.536

出版商:John Wiley&Sons, Ltd.    

年代:2003

数据来源: WILEY

ISSN:1075-2617    

DOI:10.1002/psc.524

出版商:John Wiley&Sons, Ltd.    

年代:2003

数据来源: WILEY

摘要:

AbstractThe peptaibols are a large family of membrane‐active peptides with considerable sequence homology, but with different biological properties and three‐dimensional structures. They constitute a rich resource of naturally occurring ‘mutants’ which are potentially valuable for structure/function studies of ion channels.A searchable on‐line database of sequences and structures of the peptaibols has been created athttp://www.cryst.bbk.ac.uk/peptaibol, as a resource for the biological and structural community. In this paper, the contents and organization of the website are discussed as well as procedures for submission of new entries to the database.At present, more than 300 peptaibol sequences are stored in the database. Each sequence entry contains its full literature reference and information about its biological source. Tools are provided for searching for specific peptaibol sequences or groupings of sequences, and for locating peptaibols containing specified sequence motifs. In addition the website acts as a database for structural information. The coordinates of all currently available peptaibol x‐ray and NMR structures are included and complemented, where appropriate, with molecular graphics illustrations. These include figures of model channel structures and comparisons between different peptaibol structures. The peptaibol database thus provides a tool for ready access to information and a means of investigating the sequences and structures of this class of polypeptides. Copyright © 2003 European Peptide Society and John Wil

ISSN:1075-2617    

DOI:10.1002/psc.533

出版商:John Wiley&Sons, Ltd.    

年代:2003

数据来源: WILEY

摘要:

AbstractPeptaibols and related peptide antibiotics (peptaibiotics) display diagnostically useful fragmentation patterns during mass spectrometry (FAB‐MS, ESI‐CID‐MS/MS and CID‐MSn). The paper compiles fragmentation data of pseudo‐molecular ions reported in the literature as a guide to the rational identification of recurrently isolated and new peptaibols and peptaibiotics. Taxonomic and ecological aspects of microorganisms producing peptaibols and peptaibiotics are discussed. Copyright © 2003 European Peptide Society and John Wiley

ISSN:1075-2617    

DOI:10.1002/psc.497

出版商:John Wiley&Sons, Ltd.    

年代:2003

数据来源: WILEY

摘要:

AbstractLipopeptaibols are members of a novel family of naturally occurring, short peptides with antimicrobial activity, characterized by a lipophilic acyl chain at theN‐terminus, a high content of turn/helix inducing α‐aminoisobutyric acid and a 1,2‐amino alcohol at theC‐terminus. Using solution methods, the prototypical lipopeptaibol trichogin GA IV and a large series of appropriately designed analogues were synthesized, which allow: (i) determination of the minimal lipid chain and peptide main‐chain lengths for the onset of membrane activity, and (ii) exploitation of a number of physico‐chemical techniques aimed at assessing the trichogin preferred conformation under a variety of conditions and at investigating its mechanism of interaction with the phospholipid membranes. Copyright © 2003 European Peptide Society and John Wi

ISSN:1075-2617    

DOI:10.1002/psc.500

出版商:John Wiley&Sons, Ltd.    

年代:2003

数据来源: WILEY

摘要:

AbstractTrichogin GA IV is a short lipopeptaibol antibiotic that is capable of enhancing the transport of small cations through the phospholipid double layer of the membrane. The antibiotic activity of the undecapeptide is thought to be based on either its self‐assembling or membrane‐modifying property. The chemical equilibrium between self‐aggregated and non‐aggregated molecular states was studied by CW‐ESR spectroscopy using solutions of TOAC nitroxide spin‐labelled trichogin analogues in an apolar solvent to mimic the membrane bound state. At room temperature the two different sets of signals observed in the spectrum were attributed to the presence of both monomers and aggregates in the sample. The ESR spectra of the monomeric and aggregated forms were separated and the dependence of the fraction of monomeric peptide molecules on concentration was obtained over the range 5 × 10−6to 7 × 10−4M. A two‐step aggregation mechanism is proposed: dimerization of peptide molecules followed by aggregation of dimers to assemblies of four peptide molecules per aggregate. The equilibrium constants were estimated for both steps. In addition, the lower lifetime limit was determined for dimers and tetramers. It is shown that when the peptide concentration exceeds 10−5M, the major part of the peptide molecules in solution has the form of tetrameric aggregates. Independently, the PELDOR technique was used to investigate the concentration dependence of the parameters of the dipole–dipole interaction between spin labels in frozen (77 K) glassy solutions of aggregates of mono‐labelled TOAC analogues. The number of molecules in aggregates as well as the frequency and amplitude of PELDOR signal oscillations were found to be concentration independent in the range 5 × 10−4to 8 × 10−3M. In the frozen glassy solution state, the number of peptide molecules per aggregate was determined to be close to four, which is in agreement with the value obtained for spin‐labelled trichogin at room temperature. The present data provide experimental evidence in favour of a self‐assembling rather than a membrane‐modifying ion conduction mechanism. Copyright © 2003 European Pe

ISSN:1075-2617    

DOI:10.1002/psc.513

出版商:John Wiley&Sons, Ltd.    

年代:2003

数据来源: WILEY

摘要:

AbstractRecently, the saprophytic ascomyceteSepedonium ampullosporumstrain HKI‐0053 was isolated from a basidiomycete on account of its premature induction of pigment formation inPhoma destructiva, a process often related to the neuroleptic activity of the inducing compound. The active substance was identified as the 15‐membered peptaibol type peptide Ampullosporin. Although to date more than 300 peptaibols have been discovered, their biosynthetic machinery has not been characterized yet. By improving the culture conditions it was possible to growS. ampullosporumin a submerged culture and to increase Ampullosporin production by more than three times to 33 mg/l at reduced fermentation times. The appearance of two high molecular weight proteins, HMWP1 (1.5 MDa) and HMWP2 (350 kDa) was closely related to the production of Ampullosporin during the course of fermentation. Both proteins showed a cross‐reaction with antibodies against a core fragment of nonribosomal peptide synthetases (NRPSs). Biochemical characterization of the partially purified enzymes exhibited selectivity for the substrate amino acid α‐aminoisobutyric acid (Aib), substantiating their involvement in Ampullosporin biosynthesis. Our data suggest that Ampullosporin synthetase has been isolated, and provides the basis for the characterization of the entire biosynthetic gene cluster. Furthermore, this knowledge will enable the manipulation of its NRPS template, in order to engineer mutant strains ofSepedonium ampullosporumwhich could produce more potent analogues of Ampullosporin. Copyright © 2003 European Peptide Society and John Wiley&

ISSN:1075-2617    

DOI:10.1002/psc.529

出版商:John Wiley&Sons, Ltd.    

年代:2003

数据来源: WILEY

摘要:

AbstractAmpullosporin A (AmpA), a 15mer peptaibol containing seven Aib residues is able to induce pigmentation onPhoma destructivaand hypothermia in mice, as well as to exhibit a neuroleptic effect. A circular dichroism study of ampullosporin A and its analogues was carried out in organic solvents with different polarities and detergent micelles to determine the relationship between their conformational flexibility and biological activities. The analogues were obtained by modifying theN‐ andC‐termini of ampullosporin A. Furthermore, Gln and Leu were systematically substituted by Ala and Aib residues were replaced by Ala and/or Ac6c. To estimate the helicity of the analogues, the CD spectrum of AmpA recorded in acetonitrile was correlated to its crystal structure. All analogues displayed similar CD curve shapes in organic solvents with the ratio between two negative band intensitiesR= [θ]n−π*/[θ]π−π*1 and increased helicity compared with those recorded in TFE, suggesting that the interaction of the peptides with the membrane and peptide association was necessary for their hypothermic effect. Copyright © 2003 European Peptide Society and Joh

ISSN:1075-2617    

DOI:10.1002/psc.459

出版商:John Wiley&Sons, Ltd.    

年代:2003

数据来源: WILEY

摘要:

AbstractAmpullosporin A is a 15‐mer peptaibol type polypeptide that induces pigment formation by the fungusPhoma destructiva, forms voltage‐dependent ion channels in membranes and exhibits hypothermic effects in mice. The structure of ampullosporin A has been determined by x‐ray crystallography. This is the first three‐dimensional (3D) structure of the peptaibol subfamily SF6. From theN‐terminus to residue 13 the molecule adopts an approximate right‐handed α‐helical geometry, whereas a less regular structure pattern with β‐turn characteristics is found in theC‐terminus. Even though ampullosporin A does not contain a single proline or hydroxyproline it is significantly bent. It belongs to both the shortest and the most strongly bent peptaibol 3D structures. The straight structure part encompasses residues Ac‐Trp1‐Aib10and is thus less extended than the α‐helical subunit. The 3D structure of ampullosporin A is discussed in relation to other experimentally determined peptaibol structures and in the context of its channel‐forming properties. As a part of this comparison a novel bending analysis based on a 3D curvilinear axis describing the global structural characteristics has been proposed and applied to all 3D peptaibol structures. A sampling of 2500 conformations using different molecular dynamics protocols yields, for the complete ampullosporin A structure, an α‐helix as the preferred conformationin vacuowith almost no bend. This indicates that solvent or crystal effects may be important for the experimentally observed peptide backbone bending characteristics of ampullosporin A. Copyright © 2003 European Peptide

ISSN:1075-2617    

DOI:10.1002/psc.495

出版商:John Wiley&Sons, Ltd.    

年代:2003

数据来源: WILEY

摘要:

AbstractThe crystal structures of the peptaibol antibiotics cephaibol A, cephaibol B and cephaibol C have been determined at ca. 0.9 Å resolution. All three adopt a helical conformation with a sharp bend (of about 55° ) at the central hydroxyproline. All isovalines were found to possess theDconfiguration, superposition of all four models (there are two independent molecules in the cephaibol B structure) shows that theN‐terminal helix is rigid and theC‐terminus is flexible. There are differences in the hydrogen bonding patterns for the three structures that crystallize in different space groups despite relatively similar unit cell dimensions, but only in the case of cephaibol C does the packing emulate the formation of a membrane channel believed to be important for their biological function. Copyright © 2003 European Peptide Society and John Wiley&Son

ISSN:1075-2617    

DOI:10.1002/psc.496

出版商:John Wiley&Sons, Ltd.    

年代:2003

数据来源: WILEY