Molecular and genetic characterization of a novel nisin variant produced by Streptococcus uberis

Streptococcus uberis is one of the principal causative agents of bovine mastitis. In this study, we report that S. uberis strain 42 produces a lantibiotic, nisin U, which is 78% identical (82% similar) to nisin A from Lactococcus lactis. The 15.6-kb nisin U locus comprises 11 open reading frames, similar in putative functionality but differing in arrangement from that of the nisin A biosynthetic cluster. The nisin U producer strain exhibits specific resistance (immunity) to nisin U and cross-resistance to nisin A, a finding consistent with the 55% sequence similarity of their respective immunity peptides. Homologues of the nisin U structural gene were identified in several additional S. uberis strains, and in each case cross-protective immunity was expressed to nisin A and to the other producers of nisin U and its variants. To our knowledge, this is the first report both of characterization of a bacteriocin by S. uberis, as well as of a member of the nisin family of peptides in a species other than L. lactis.     

Spontaneous and promoted association of linear oligoglycines

Linear oligoglycines of various lengths bearing a carboxyl or an amide group at their C-termini and also their poly(acrylamide) conjugates were synthesized. No self-assembly into supramolecular structures was observed for free oligoglycines H-(Gly)m-OH(m = 3-5). At the same time, oligoglycylamides H-(Gly)m-NH2 (m = 3-5) demonstrated ability for both self-assembly in aqueous solution and assembly promoted by an additional interaction with surface. In the case of polymer-bound oligoglycines (and their amides), no intramolecular clustering of peptide chains, as expected, was observed. This means that the presence of several oligoglycine chains bound to each other in one center is not a necessary prerequisite for polyglycine II-type association.     

The STAR project: context, objectives and approaches

STAR is a European Commission Framework V project (EVK1-CT-2001-00089). The project aim is to provide practical advice and solutions with regard to many of the issues associated with the Water Framework Directive. This paper provides a context for the STAR research programme through a review of the requirements of the directive and the Common Implementation Strategy responsible for guiding its implementation. The scientific and strategic objectives of STAR are set out in the form of a series of research questions and the reader is referred to the papers in this volume that address those objectives, which include: (a) Which methods or biological quality elements are best able to indicate certain stressors? (b) Which method can be used on which scale? (c) Which method is suited for early and late warnings? (d) How are different assessment methods affected by errors and uncertainty? (e) How can data from different assessment methods be intercalibrated? (f) How can the cost-effectiveness of field and laboratory protocols be optimised? (g) How can boundaries of the five classes of Ecological Status be best set? (h) What contribution can STAR make to the development of European standards? The methodological approaches adopted to meet these objectives are described. These include the selection of the 22 stream-types and 263 sites sampled in 11 countries, the sampling protocols used to sample and survey phytobenthos, macrophytes, macroinvertebrates, fish and hydromorphology, the quality control and uncertainty analyses that were applied, including training, replicate sampling and audit of performance, the development of bespoke software and the project outputs. This paper provides the detailed background information to be referred to in conjunction with most of the other papers in this volume. These papers are divided into seven sections: (1) typology, (2) organism groups, (3) macrophytes and diatoms, (4) hydromorphology, (5) tools for assessing European streams with macroinvertebrates, (6) intercalibration and comparison and (7) errors and uncertainty. The principal findings of the papers in each section and their relevance to the Water Framework Directive are synthesised in short summary papers at the beginning of each section. Additional outputs, including all sampling and laboratory protocols and project deliverables, together with a range of freely downloadable software are available from the project website at www.eu_star.at.     

Neue Materialien zur Flora Bulgariens

Ohne Zusammenfassung     

The action of Con-ikot-ikot toxin on single AMPA-type glutamate receptors

Conotoxins are a large group of naturally occurring toxic peptides produced by the predatory sea snails of the genus Conus. Many of these toxins target ion channels, often with high specificity and affinity. As such, they have proven to be invaluable for basic research, as well as acting as leads for therapeutic strategies. Con-ikot-ikot is the only conotoxin so far identified that targets AMPA-type glutamate receptors, the main mediators of excitatory neurotransmission in the vertebrate brain. Here, we describe how the toxin modifies the activity of AMPA receptors at the single-channel level. The toxin binds to the AMPA receptor with EC₅₀ of 5 nM, and once bound takes minutes to wash out. As shown previously, it effectively blocks desensitization of AMPA receptors; however, compared to other desensitization blockers, it is a poor stabilizer of the open channel because toxin-bound AMPA receptors undergo frequent brief closures. We propose that this is a direct consequence of the toxin’s unique binding mode to the ligand-binding domains (LBDs). Unlike other blockers of desensitization, which stabilize individual dimers within an AMPA receptor tetramer, the toxin immobilizes all four LBDs of the tetramer. This result further emphasizes that quaternary reorganization of independent LBD dimers is essential for the full activity of AMPA receptors.     

Structure and properties of G84R and L99M mutants of human small heat shock protein HspB1 correlating with motor neuropathy

Some properties of G84R and L99M mutants of HspB1 associated with peripheral distal neuropathies were investigated. Homooligomers formed by these mutants are larger than those of the wild type HspB1. Large oligomers of G84R and L99M mutants have compromised stability and tend to dissociate at low protein concentration. G84R and L99M mutations promote phosphorylation-dependent dissociation of HspB1 oligomers without affecting kinetics of HspB1 phosphorylation by MAPKAP2 kinase. Both mutants weakly interact with HspB6 forming small heterooligomers and being unable to form large heterooligomers characteristic for the wild type HspB1. G84R and L99M mutants possess lower chaperone-like activity than the wild type HspB1 with several model substrates. We suggest that G84R mutation affects mobility and accessibility of the N-terminal domain thus modifying interdimer contacts in HspB1 oligomers. The L99M mutation is located within the hydrophobic core of the α-crystallin domain close to the key R140 residue, and could affect the dimer stability.     

ITO‐Free,Small‐Molecule Organic Solar Cells on Spray‐Coated Copper‐Nanowire‐Based Transparent Electrodes

The great potential of solution‐processed metal nanowire networks utilized as a transparent electrode has attracted much attention in the last years. Typically, silver nanowires are applied, although their replacement by more abundant and cheaper materials is of interest. Here, a hydrazine‐free synthesis route for high aspect ratio copper nanowires is used to prepare conductive networks showing an enhanced electrode performance. The network deposition is done with a scalable spray‐coating process on glass and on polymer foils. By a pressing or an annealing step, highly conductive transparent electrodes are obtained, and they reveal transmittance‐resistance values similar to indium tin oxide (ITO) and networks made of silver nanowires. The application potential of the copper nanowire electrodes is demonstrated by integrating them into an evaporated small‐molecule organic solar cell with 3% efficiency.     

Analyzing Protein Dynamics Using Hydrogen Exchange Mass Spectrometry

All cellular processes depend on the functionality of proteins. Although the functionality of a given protein is the direct consequence of its unique amino acid sequence, it is only realized by the folding of the polypeptide chain into a single defined three-dimensional arrangement or more commonly into an ensemble of interconverting conformations. Investigating the connection between protein conformation and its function is therefore essential for a complete understanding of how proteins are able to fulfill their great variety of tasks. One possibility to study conformational changes a protein undergoes while progressing through its functional cycle is hydrogen-¹H/²H-exchange in combination with high-resolution mass spectrometry (HX-MS). HX-MS is a versatile and robust method that adds a new dimension to structural information obtained by e.g. crystallography. It is used to study protein folding and unfolding, binding of small molecule ligands, protein-protein interactions, conformational changes linked to enzyme catalysis, and allostery. In addition, HX-MS is often used when the amount of protein is very limited or crystallization of the protein is not feasible. Here we provide a general protocol for studying protein dynamics with HX-MS and describe as an example how to reveal the interaction interface of two proteins in a complex.