Analysis of the capacitive coupling of Josephson transmissions lines

We study the capacitive coupling of two long Josephson junctions by imposing appropriate boundary conditions at the ends of the junctions. Numerical simulations show good agreement with analytical estimates of the parameter range for which reflections of fluxons at the coupled end of the junction occur. We discuss our results in terms of recent experiments concerning phase‐locking phenomena in Josephson junctions fluxon oscillators devices

Characterisation of single domain ATP-binding cassette protein homologues of Theileria parva

Two distinct genes encoding single domain, ATP-binding cassette transport protein homologues of Theileria parva were cloned and sequenced. Neither of the genes is tandemly duplicated. One gene, TpABCI, encodes a predicted protein of 593 amino acids with an N-terminal hydrophobic domain containing six potential membrane-spanning segments. A single discontinuous ATP-binding element was located in the C-terminal region of TpABCI. The second gene, TpABC2, also contains a single C-terminal ATP-binding motif. Copies of TpABC2 were present at four loci in the T. parva genome on three different chromosomes. TpABCI exhibited allelic polymorphism between stocks of the parasite. Comparison of cDNA and genomic sequences revealed that TpABCl contained seven short introns, between 29 and 84 bp in length. The full-length TpABCI protein was expressed in insect cells using the baculovirus system. Application of antibodies raised against the recombinant antigen to western blots of T. parva piro-plasm lysates detected an 85 kDa protein in this life-cycle stage

Screening for Theileria parva secretory gene products by functional analysis in Saccharomyces cerevisiae

Molecules located on cell surfaces and those that are secreted from the cell frequently play a critical role in cell biology by mediating interaction with the external environment. These types of parasite molecules often constitute targets for protective host immune responses and are thus of additional interest as candidate vaccine antigens. Targeting of proteins to an extra-cellular environment usually involves trafficking through components of the secretory pathway. Most proteins access this pathway via insertion into or translocation across the endoplasmic reticulum, a process dependent on a signal sequence at or close to the N-terminus that exhibits conserved features across a wide range of eukaryotic organisms, although the signals are degenerate in amino acid sequence (1-3). The secretory signal sequences of proteins from different organisms are functionally interchangeable, highlighting the conserved nature of the secretory apparatus (4). These observations led to the development of a 'signal sequence trap' (SST) methodology to identify secretory molecules by expression screens in a heterologous system (5). Export of a few eukaryotic proteins occurs by a different mechanism (1) and these exceptions to the general rule would not be expected to function in the SST system. The original SST method used a COS cell expression cloning system and depends on complementation of a deleted signal sequence on a gene encoding the chain of human interleukin-2 receptor (5). This system is dependent on successive rounds of enrichment of plasmid recovered from transfected cells and has been used to identify many novel higher eukaryotic secretory proteins (5,6) including secreted proteins from the salivary glands of Anopheles gambiae (7). A simplified SST method has been described that exploits the requirement of a secreted enzyme in permitting growth of Saccharomyces cerevisiae when sucrose is the sole carbon source (8,9). The yeast SST system has identified previously characterised human proteins containing a cleaved or non-cleaved secretory signal sequence and proteins that are targeted to intracellular organelles (9), indicating flexibility of the method and predicting identification of a wide repertoire of secretory proteins. It has also been used to identify secretory proteins of Drosophila (10) and Arabidopsis (11). In this report we examine the suitability of one of two yeast SSt system (8,9) for the identification of secretory proteins from Theileria parva, an intracellular protozoan pathogen that usually causes a lethal disease in cattle known as East Coast fever (ECF) (12)

Theileria parva genomics reveals an atypical apicomplexan genome

The discipline of genomics is setting new paradigms in research approaches to resolving problems in human and animal health. We propose to determine the genome sequence of Theileria parva, a pathogen of cattle, using the random shotgun approach pioneered at The Institute for Genomic Research (TIGR). A number of features of the T. parva genome make it particularly suitable for this approach. The G+C content of genomic DNA is about 31 percent, non-coding repetitive DNA constitute less than 1 percent of total DNA and a framework for the 10-12 Mbp genome is available in the form of a physical map for all four chromosomes. Minisatellite sequences are the only dispersed repetitive sequences identified so far, but they are limited in distribution to 13 of 33 SfiI fragments. Telomere and sub-telomeric non-coding sequences occupy less than 10 kbp at each chromosomal end and there are only two units encoding cytoplasmic rRNAs. Three sets of distinct multicopy sequences encoding ORFs have been identified but it is not known if these are associated with expression of parasite antigenic diversity. Protein coding genes exhibit a bias in codon usage and introns when present are unusually short. Like other apicomplexan organisms, T. parva contains two extrachromosomal DNAs, a mitochondrial DNA and a plastid DNA molecule. By annotating the gnome sequence, in combination with the use of microarray technology and comparative genomics, we expect to gain significant insights into unique aspects of the biology of T. parva. We believe that the data will underpin future research to aid in the identification of targets of protective CD8 + cell mediated immune responses, and parasite molecules involved in inducing reversible host leukocyte transformation and tumour-like behaviour of transformed parasitised cells

Identification of candidate sialome components expressed in ixodid tick salivary glands using secretion signal complementation in mammalian cells

Ixodid ticks manipulate mammalian host pathways by secreting molecules from salivary glands. Novel cDNAs containing functional secretion signals were isolated from ixodid tick salivary glands using a signal sequence trap. Only 15/61 Rhipicephalus appendiculatus and 1/7 Amblyomma variegatum cDNAs had significant identity (< 1e-15) to previously identified sequences. Polypeptides that may interact with host pathways included a kinase inhibitor. Two proteins encoded homologues of the yolk protein vitellogenin and seventeen contained glycine-rich motifs. Four proteins without sequence matches had conserved structural folds, identified using a Threading algorithm. Predicted secretion signals were between fifteen and fifty-seven amino acids long. Four homologous polymorphic proteins contained conserved (26/27 residues) signal peptides. Ten functional tick secretion signals could not be unambiguously identified using predictive algorithms