rabbit
not annotated - annotated - LINNAEUS only
20971901
Mapping of the Neisseria meningitidis NadA cell-binding site: relevance of predicted {alpha}-helices in the NH2-terminal and dimeric coiled-coil regions.
NadA is a trimeric autotransporter protein of Neisseria meningitidis belonging to the group of oligomeric coiled-coil adhesins. It is implicated in the colonization of the human upper respiratory tract by hypervirulent serogroup B N. meningitidis strains and is part of a multiantigen anti-serogroup B vaccine. Structure prediction indicates that NadA is made by a COOH-terminal membrane anchor (also necessary for autotranslocation to the bacterial surface), an intermediate elongated coiled-coil-rich stalk, and an NH(2)-terminal region involved in cell interaction. Electron microscopy analysis and structure prediction suggest that the apical region of NadA forms a compact and globular domain. Deletion studies proved that the NH(2)-terminal sequence (residues 24 to 87) is necessary for cell adhesion. In this study, to better define the NadA cell binding site, we exploited (i) a panel of NadA mutants lacking sequences along the coiled-coil stalk and (ii) several oligoclonal rabbit antibodies, and their relative Fab fragments, directed to linear epitopes distributed along the NadA ectodomain. We identified two critical regions for the NadA-cell receptor interaction with Chang cells: the NH(2) globular head domain and the NH(2) dimeric intrachain coiled-coil alpha-helices stemming from the stalk. This raises the importance of different modules within the predicted NadA structure. The identification of linear epitopes involved in receptor binding that are able to induce interfering antibodies reinforces the importance of NadA as a vaccine antigen.
21699595
Host translational control of a polydnavirus, Cotesia plutellae bracovirus, by sequestering host eIF4A to prevent formation of a translation initiation complex.
Host translational control is a viral strategy to exploit host cellular resources. Parasitization by some endoparasitoids containing polydnaviruses inhibits the synthesis of specific host proteins at post-transcriptional level. Two host translation inhibitory factors (HTIFs) have been proposed in Cotesia plutellae bracovirus (CpBV). Parasitization by C. plutellae inhibited storage protein 1 (SP1) synthesis of Plutella xylostella at post-transcriptional level. One HTIF, CpBV15Beta, inhibited the translation of SP1 mRNA in an in vitro translation assay using rabbit reticulocyte lysate, but did not inhibit its own mRNA. To further analyse the discrimination of target and nontarget mRNAs of the inhibitory effect of HTIF, 5' untranslated regions (UTRs) of SP1 and CpBV15Beta mRNA were reciprocally exchanged. In the presence of HTIFs, the chimeric CpBV15Beta mRNA that contained SP1 5' UTR was not translated, whereas the chimeric SP1 mRNA that contained CpBV15Beta 5' UTR was translated. There was a difference in the 5' UTR secondary structures between target (SP1) and nontarget (CpBV15alpha and CpBV15Beta) mRNAs in terms of thermal stability. Different mutant 5' UTRs of SP1 mRNA were prepared by point mutations to modify their secondary structures. The constructs containing 5' UTRs of high thermal stability in their secondary structures were inhibited by HTIF, but those of low thermal stability were not. Immunoprecipitation with CpBV15Beta antibody coprecipitated eIF4A, which would be required for unwinding the secondary structure of the 5' UTR. These results indicate that the viral HTIF discriminates between host mRNAs according to their dependency on eIF4A to form a functional initiation complex for translation.
21047955
Alphacoronavirus transmissible gastroenteritis virus nsp1 protein suppresses protein translation in mammalian cells and in cell-free HeLa cell extracts but not in rabbit reticulocyte lysate.
The nsp1 protein of transmissible gastroenteritis virus (TGEV), an alphacoronavirus, efficiently suppressed protein synthesis in mammalian cells. Unlike the nsp1 protein of severe acute respiratory syndrome coronavirus, a betacoronavirus, the TGEV nsp1 protein was unable to bind 40S ribosomal subunits or promote host mRNA degradation. TGEV nsp1 also suppressed protein translation in cell-free HeLa cell extract; however, it did not affect translation in rabbit reticulocyte lysate (RRL). Our data suggested that HeLa cell extracts and cultured host cells, but not RRL, contain a host factor(s) that is essential for TGEV nsp1-induced translational suppression.